
:''For other uses, see DNA (disambiguation).'' Deoxyribonucleic acid (DNA) or deoxyribose nucleic acid is a nucleic acid that contains the genetics instructions specifying the developmental biology of all cellular forms of life (and many viruses). DNA is often referred to as the molecule of heredity, as it is responsible for the genetic propagation of most biological inheritance traits. During reproduction, DNA is DNA replication and transmitted to the offspring. In bacterium and other prokaryote biological cell organisms, DNA is not separated from the cytoplasm by a nuclear envelope. In the eukaryote cells that make up plants, animals and in other multi-cellular organisms, by contrast, most of the DNA is located in the cell nucleus. The energy-generating organelles known as chloroplasts and mitochondria also carry DNA, as do many viruses. == DNA in brief == This section presents a brief and simple overview of DNA. * Genes can be loosely viewed as the organism's "cookbook"; * A strand of DNA contains genes, areas that gene regulation, and areas that either have no function, or a function junk DNA; * DNA is organized as two complementary strands, head-to-toe, with bonds between them that can be "unzipped" like a zipper, separating the strands; * DNA is encoded with four interchangeable "building blocks", called "base pair ", which can be abbreviated Adenine, Thymine, Cytosine, and Guanine; each base "pairs up" with only one other base: A+T, T+A, C+G and G+C; that is, an "A" on one strand of double-stranded DNA will "mate" properly only with a "T" on the other, complementary strand; * The order does matter: A+T is not the same as T+A, just as C+G is not the same as G+C; * However, since there are just four possible combinations, naming only one base on the conventionally chosen side of the strand is enough to describe the sequence; * The order of the bases along the length of the DNA is what it's all about, the DNA sequence itself is the description for genes; * DNA replication is performed by splitting (unzipping) the double strand down the middle via relatively trivial chemical reactions, and recreating the "other half" of each new single strand by drowning each half in a "soup" made of the four bases. Since each of the "bases" can only combine with one other base, the base on the old strand dictates which base will be on the new strand. This way, each split half of the strand plus the bases it collects from the soup will ideally end up as a complete replica of the original, unless a mutation occurs; * Mutations are simply chemical imperfections in this process: a base is accidentally skipped, inserted, or incorrectly copied, or the chain is trimmed, or added to; all other basic mutations can be described as combinations of these accidental "operations". ==DNA in crime== Forensic science can use DNA located in blood, semen, or hair left at the scene of a crime to identify a possible suspect, a process called DNA profiling or genetic fingerprinting. In DNA profiling the relative lengths of sections of repetitive DNA, such as short tandem repeats and minisatellites, are compared. DNA profiling was developed in 1984 by English geneticist Alec Jeffries, and was first used in 1986 in the Enderby murders case in Leicestershire, England. Many jurisdictions require convicts of certain types of crimes to provide a sample of DNA for inclusion in a computerized database. This has helped investigators solve old cases where the perpetrator was unknown and only a DNA sample was obtained from the scene (particularly in rape cases between strangers). This method is one of the most reliable techniques for identifying a criminal, but is not always perfect, for example if no DNA can be retrieved, or if the scene is contaminated with the DNA of several possible suspects. == Overview of molecular structure == [[Image:DNA-structure-and-bases.png|right|thumb|Schematic representation of the DNA which illustrates its double helix structure]] Although sometimes called "the molecule of heredity", pieces of DNA as people typically think of them are not single molecules. Rather, they are pairs of molecules, which entwine like vines to form a double helix (see the illustration at the right). Each vine-like molecule is a strand of DNA: a chemically linked chain of nucleotides, each of which consists of a sugar, a phosphate and one of four kinds of nucleobases ("bases"). Because DNA strands are composed of these nucleotide subunits, they are polymers. The diversity of the bases means that there are four kinds of nucleotides, which are commonly referred to by the identity of their bases. These are adenine (A), thymine (T), cytosine (C), and guanine (G). In a DNA double helix, two polynucleotide strands can associate through the hydrophobic effect. Specificity of which strands stay associated is determined by base pair. Each base forms hydrogen bonds readily to only one other -- A to T and C to G -- so that the identity of the base on one strand dictates the strength of the association; the more complementary bases exist, the stronger and longer-lasting the association. The cell's machinery is capable of ''melting'' or disassociating a DNA double helix, and using each DNA strand as a template for synthesizing a new strand which is nearly identical to the previous strand. Errors that occur in the synthesis are known as mutations. The process known as PCR mimics this process in vitro in a nonliving system. Because pairing causes the nucleotide bases to face the helical axis, the sugar and phosphate groups of the nucleotides run along the outside; the two chains they form are sometimes called the "backbones" of the helix. In fact, it is chemical bonds between the phosphates and the sugars that link one nucleotide to the next in the DNA strand. ==The role of the sequence== Within a gene, the sequence of nucleotides along a DNA strand defines a protein, which an organism is liable to manufacture or "gene expression" at one or several points in its life using the information of the sequence. The relationship between the nucleotide sequence and the amino acid sequence of the protein is determined by simple cellular rules of Translation (biology), known collectively as the genetic code. The genetic code is made up of three-letter 'words' (termed a codon) formed from a sequence of three nucleotides (e.g. ACT, CAG, TTT). These codons can then be translated with messenger RNA and then transfer RNA, with a codon corresponding to a particular amino acid. Since there are 64 possible codons, most amino acids have more than one possible codon. There are also three 'stop' or 'nonsense' codons signifying the end of the coding region. In many species of organism, only a small fraction of the total sequence of the genome appears to encode protein. The function of the rest is a matter of speculation. It is known that certain nucleotide sequences specify affinity for DNA binding proteins, which play a wide variety of vital roles, in particular through control of replication and transcription. These sequences are frequently called regulatory sequences, and researchers assume that so far they have identified only a tiny fraction of the total that exist. "Junk DNA" represents sequences that do not yet appear to contain genes or to have a function. Sequence also determines a DNA segment's susceptibility to cleavage by restriction enzymes, the quintessential tools of genetic engineering. The position of cleavage sites throughout an individual's genome determines one kind of an individual's "DNA fingerprinting". ==DNA replication== ''Main article:'' DNA replication DNA replication or DNA synthesis is the process of copying the double-stranded DNA prior to cell division. The two resulting double strands are generally almost perfectly identical, but occasionally errors in replication can result in a less than perfect copy (see mutation), and each of them consists of one original and one newly synthesized strand. This is called ''semiconservative replication''. The process of replication consists of three steps: ''initiation'', ''replication'' and ''termination''. ==Mechanical properties relevant to biology== see Mechanical properties of DNA. ===Strands association and dissociation=== The hydrogen bonds between the strands of the double helix are weak enough that they can be easily separated by enzymes. Enzymes known as helicases unwind the strands to facilitate the advance of sequence-reading enzymes such as DNA polymerase. The unwinding requires that helicases chemically cleave the phosphate backbone of one of the strands so that it can swivel around the other. The strands can also be separated by gentle heating, as used in PCR, provided they have fewer than about 10,000 base pairs (10 kilobase pairs, or 10 kbp). The intertwining of the DNA strands makes long segments difficult to separate. ===Circular DNA=== When the ends of a piece of double-helical DNA are joined so that it forms a circle, as in plasmid DNA, the strands are knot theory knotted. This means they cannot be separated by gentle heating or by any process that does not involve breaking a strand. The task of unknotting topologically linked strands of DNA falls to enzymes known as topoisomerases. Some of these enzymes unknot circular DNA by cleaving two strands so that another double-stranded segment can pass through. Unknotting is required for the replication of circular DNA as well as for various types of recombination in linear DNA. ===Great length versus tiny breadth=== The narrow breadth of the double helix makes it impossible to detect by conventional transmission electron microscope, except by heavy staining. At the same time, the DNA found in many cells can be macroscopic in length -- approximately 5 centimetres long for strands in a human chromosome. Consequently, cells must compact or "package" DNA to carry it within them. This is one of the functions of the chromosomes, which contain spool-like proteins known as histones, around which DNA winds. ===Different helix geometries=== The DNA helix can assume one of three slightly different geometries, of which the "B" form described by James D. Watson and Francis Crick is believed to predominate in cells. It is 2 nanometres wide and extends 3.4 nanometres per 10 Base pair of sequence. This is also the approximate length of sequence in which the double helix makes one complete turn about its axis. This frequency of twist (known as the helical ''pitch'') depends largely on stacking forces that each base exerts on its neighbors in the chain. ====Supercoiled DNA==== The B form of the DNA helix twists 360° per 10.6 bp in the absence of strain. But many molecular biological processes can induce strain. A DNA segment with excess or insufficient helical twisting is referred to, respectively, as positively or negatively "supercoil". DNA ''in vivo'' is typically negatively supercoiled, which facilitates the unwinding of the double-helix required for transcription. ====Conditions for formation of A and Z helices==== The two other known double-helical forms of DNA, called A and Z-DNA, differ modestly in their geometry and dimensions. The A form appears likely to occur only in dehydrated samples of DNA, such as those used in crystallography experiments, and possibly in hybrid pairings of DNA and RNA strands. Segments of DNA that cells have methylation for regulatory purposes may adopt the Z geometry, in which the strands turn about the helical axis like a mirror image of the B form. ====Table of comparison of the properties of different helical forms==== {| border="0" align="center" style="border: 1px solid #999; background-color:#FFFFFF" |-align="center" bgcolor="#CCCCCC" !Geometry attribute !A-form !B-form !Z-form |- |Helix sense ||align="center"| right-handed ||align="center"| right-handed ||align="center"| left-handed |--bgcolor="#EFEFEF" |Repeating unit ||align="right"| 1 bp ||align="right"| 1 bp ||align="right"| 2 bp |----- |Rotation/bp ||align="right"| 33.6° ||align="right"| 35.9° ||align="right"| 60°/2 |--bgcolor="#EFEFEF" |Mean bp/turn ||align="right"| 10.7 ||align="right"| 10.0 ||align="right"| 12 |----- |Inclination of bp to axis ||align="right"| +19° ||align="right"| -1.2° ||align="right"| -9° |--bgcolor="#EFEFEF" |Rise/bp along axis ||align="right"| 0.23 nm ||align="right"| 0.332 nm ||align="right"| 0.38 nm |----- |Pitch/turn of helix ||align="right"| 2.46 nm ||align="right"| 3.32 nm ||align="right"| 4.56 nm |--bgcolor="#EFEFEF" |Mean propeller twist ||align="right"| +18° ||align="right"| +16° ||align="right"| 0° |----- |Glycosyl angle ||align="center"| anti ||align="center"| anti ||align="center"| C: anti,
G: syn |--bgcolor="#EFEFEF" |Sugar pucker ||align="center"| C3'-endo ||align="center"| C2'-endo ||align="center"| C: C2'-endo,
G: C2'-exo |----- |Diameter ||align="right"| 260 nm ||align="right"| 200 nm ||align="right"| 180 nm |--bgcolor="#EFEFEF" |} ===Non-helical forms=== Other, including non-helical, forms of DNA have been described, for example a side-by-side (SBS) configuration. Indeed, it is far from certain that the B-form double helix is the dominant form in living cells. ==Direction of DNA strands== The asymmetric shape and linkage of nucleotides means that a DNA strand always has a discernible orientation or directionality. Because of this directionality, close inspection of a double helix reveals that nucleotides are heading one way along one strand (the "''ascending strand''"), and the other way along the other strand (the "''descending strand''"). This arrangement of the strands is called antiparallel. ===Chemical nomenclature (5' and 3')=== For reasons of chemical nomenclature, people who work with DNA refer to the asymmetric ends of each strand as the '''5%27_end and 3%27_end ends (pronounced \"five prime\" and \"three prime\"). DNA workers and enzymes alike always read nucleotide sequences in the \"5%27_end to 3%27_end direction'''". In a vertically oriented double helix, the 3%27_end strand is said to be ascending while the 5' strand is said to be descending. ===Sense and antisense=== As a result of their antiparallel arrangement and the sequence-reading preferences of enzymes, even if both strands carried identical instead of complementary sequences, cells could properly translate only one of them. The other strand a cell can only read backwards. molecular biology call a sequence "sense" if it is translated or translatable, and they call its complement "antisense". It follows then, somewhat paradoxically, that the template for transcription is the ''antisense'' strand. The resulting transcript is an RNA replica of the ''sense'' strand and is itself ''sense.'' ===An exception: viruses=== Some viruses blur the distinction between sense and antisense, because certain sequences of their genome do double duty, encoding one protein when read 5' to 3' along one strand, and a second protein when read in the opposite direction along the other strand. As a result, the genomes of these viruses are unusually compact for the number of genes they contain, which biologists view as an adaptation (biology). ===As viewed by topologists=== Topologists like to note that the juxtaposition of the 3%27_end end of one DNA strand beside the 5%27_end end of the other at both ends of a double-helical segment makes the arrangement a "crab canon". ==Single-stranded DNA (ssDNA) and repair of mutations== In some viruses DNA appears in a non-helical, single-stranded form. Because many of the DNA repair mechanisms of cells work only on paired bases, viruses that carry single-stranded DNA genomes mutation more frequently than they would otherwise. As a result, such species may adapt more rapidly to avoid extinction. The result would not be so favorable in more complicated and more slowly replicating organisms, however, which may explain why only viruses carry single-stranded DNA. These viruses presumably also benefit from the lower cost of replicating one strand versus two. ==The history of DNA research== [[Image:JamesWatson.jpg|thumb|200px|James D. Watson in the Cavendish Laboratory at the University of Cambridge]] The discovery that DNA was the carrier of genetic information was a process which required many earlier discoveries. The existence of DNA was discovered in the mid 19th century. However, it was only in the early 20th century that researchers began suggesting that it might store genetic information. This was only accepted after the structure of DNA was elucidated by Watson and Crick, which they published in 1953. Watson and Crick proposed the central dogma of molecular biology in 1957, describing the process whereby proteins are produced from cell nucleus DNA. ===First isolation of DNA=== Working in the 19th century, biochemists initially isolated DNA and RNA (mixed together) from cell nuclei. They were relatively quick to appreciate the polymeric nature of their "nucleic acid" isolates, but realized only later that nucleotides were of two types--one containing ribose and the other deoxyribose. It was this subsequent discovery that led to the identification and naming of DNA as a substance distinct from RNA. Friedrich Miescher (1844-1895) discovered a substance he called "nuclein" in 1869. Somewhat later, he isolated a pure sample of the material now known as DNA from the sperm of salmon, and in 1889 his pupil, Richard Altmann, named it "nucleic acid". This substance was found to exist only in the chromosomes. ===Establishing a link between heritable traits and chromosomes=== Max Delbrück, Nikolai V. Timofeeff-Ressovsky, and Karl G. Zimmer published results in 1935 suggesting that chromosomes are very large molecules the structure of which can be changed by treatment with X-rays, and that by so changing their structure it was possible to change the heritable characteristics governed by those chromosomes. (Delbrück and Salvador Luria were awarded the Nobel Prize in 1969 for their work on the genetic structure of viruses.) In 1943, Oswald Theodore Avery discovered that traits proper to the "smooth" form of the ''Pneumococcus'' could be transferred to the "rough" form of the same bacteria merely by making the killed "smooth" (S) form available to the live "rough" (R) form. Quite unexpectedly, the living R ''Pneumococcus'' bacteria were transformed into a new strain of the S form, and the transferred S characteristics turned out to be heritable. Avery called the medium of transfer of traits the transforming principle; he identified DNA as the transforming principle, and not protein as previously thought. In 1953, Alfred Hershey and Martha Chase did an experiment Hershey-Chase experiment that showed, in T2 phage, that DNA is the genetic material (Hershey shared the Nobel prize with Luria). [[Image:FirstSketchOfDNADoubleHelix.jpg|thumb|200px|Francis Crick's first sketch of the deoxyribonucleic acid double-helix pattern]] In 1944, the renowned physicist, Erwin Schrödinger, published a brief book entitled ''What is Life?'', where he maintained that chromosomes contained what he called the "hereditary code-script" of life. He added: "But the term code-script is, of course, too narrow. The chromosome structures are at the same time instrumental in bringing about the development they foreshadow. They are law-code and executive power -- or, to use another simile, they are architect's plan and builder's craft -- in one." He conceived of these dual functional elements as being woven into the molecular structure of chromosomes. By understanding the exact molecular structure of the chromosomes one could hope to understand both the "architect's plan" and also how that plan was carried out through the "builder's craft." Francis Crick, James D. Watson, Maurice Wilkins, Rosalind Franklin, Seymour Benzer, ''et al''., took up the physicist's challenge to work out the structure of the chromosomes and the question of how the segments of the chromosomes that were conceived to relate to specific traits could possibly do their jobs. Just how the presence of specific features in the molecular structure of chromosomes could produce traits and behaviors in living organisms was unimaginable at the time. Because chemical dissection of DNA samples always yielded the same four nucleotides, the chemical composition of DNA appeared simple, perhaps even uniform. Organisms, on the other hand, are fantastically complex individually and widely diverse collectively. Geneticists did not speak of genes as conveyors of "information" in such words, but if they had, they would not have hesitated to quantify the amount of information that genes need to convey as vast. The idea that information might reside in a chemical in the same way that it exists in text--as a finite alphabet of letters arranged in a sequence of unlimited length--had not yet been conceived. It would emerge upon the discovery of DNA's structure, but few researchers imagined that DNA's structure had much to say about genetics. ===Discovery of the structure of DNA=== In the 1950s, only a few groups made it their goal to determine the structure of DNA. These included an American group led by Linus Pauling, and two groups in Britain. At the University of Cambridge, Crick and Watson were building physical models using metal rods and balls, in which they incorporated the known chemical structures of the nucleotides, as well as the known position of the linkages joining one nucleotide to the next along the polymer. At King's College, London, Maurice Wilkins and Rosalind Franklin were examining crystallography patterns of DNA fibers. ====Discovery that DNA is helical==== A key inspiration in the work of all of these teams was the discovery in 1948 by Pauling that many proteins included helical (see alpha helix) shapes. Pauling had deduced this structure from X-ray patterns. Even in the initial crude diffraction data from DNA, it was evident that the structure involved helices. But this insight was only a beginning. There remained the questions of how many strands came together, whether this number was the same for every helix, whether the bases pointed toward the helical axis or away, and ultimately what were the explicit angles and coordinates of all the bonds and atoms. Such questions motivated the modeling efforts of Watson and Crick. ====Discovery that complementary nucleotides occur in equal proportions==== In their modeling, Watson and Crick restricted themselves to what they saw as chemically and biologically reasonable. Still, the breadth of possibilities was very wide. A breakthrough occurred in 1952, when Erwin Chargaff visited Cambridge and inspired Crick with a description of experiments Chargaff had published in 1947. Chargaff had observed that the proportions of the four nucleotides vary between one DNA sample and the next, but that for particular pairs of nucleotides -- adenine and thymine, guanine and cytosine -- the two nucleotides are always present in equal proportions. ====Watson and Crick's model==== [[Image:DNA Model Crick-Watson.jpg|thumb|200px|right|Crick and Watson DNA model built in 1953, currently on display at the National Science Museum in London.]] James Watson and Francis Crick had begun to contemplate double helical arrangements, and they saw that by reversing the directionality of one strand with respect to the other, they could provide an explanation for Chargaff's puzzling finding. This explanation was the complementary pairing of the bases, which also had the effect of ensuring that the distance between the phosphate chains did not vary along a sequence. Watson and Crick were able to discern that this distance was constant and to measure its exact value of 2 nanometres from an X-ray pattern obtained by Franklin. The same pattern also gave them the 3.4 nanometre-per-10 bp "pitch" of the helix. The pair quickly converged upon a model, which they announced before Franklin herself published any of her work. The great assistance Watson and Crick derived from Franklin's data has become a subject of controversy, and it has angered people who believe Franklin has not received the credit due to her. The most controversial aspect is that Franklin's critical X-ray pattern was shown to Watson and Crick without Franklin's knowledge or permission. Wilkins showed it to them at his lab while Franklin was away. ====Publishing of the "Central Dogma"==== Watson and Crick's model attracted great interest immediately upon its presentation. Arriving at their conclusion on February 21 1953, Watson and Crick made their first announcement on February 28. Their paper [http://www.nature.com/genomics/human/watson-crick/ 'A Structure for Deoxyribose Nucleic Acid'] was published on April 25. In an influential presentation in 1957, Crick laid out the "Central Dogma", which foretold the relationship between DNA, RNA, and proteins, and articulated the "sequence hypothesis." A critical confirmation of the replication mechanism that was implied by the double-helical structure followed in 1958 in the form of the Meselson-Stahl experiment. Work by Crick and coworkers deciphered the genetic code not long afterward. These findings represent the birth of molecular biology. James D. Watson, Francis Crick, and Maurice Wilkins were awarded the 1962 Nobel Prize for Medicine for discovering the molecular structure of DNA, by which time Rosalind Franklin had died. Nobel prizes are not awarded posthumously. ==Bibliography== * ''DNA: The Secret of Life'', by James D. Watson. ISBN 0-375-41546-7 ==External links== *[http://nist.rcsb.org/pdb/molecules/pdb23_1.html DNA: PDB molecule of the month] * *[http://www.rotten.com/library/medicine/dna/ Rotten Library] Article on DNA *[http://news.bbc.co.uk/1/hi/sci/tech/2949629.stm 17 April, 2003, BBC News: Most ancient DNA ever?] *Watson, James, and Francis Crick, "''[http://biocrs.biomed.brown.edu/Books/Chapters/Ch%208/DH-Paper.html Molecular structure of nucleic acids], A structure for Deoxyribose Nucleic Acid''". April 2, 1953. (paper on the structure of DNA) *[http://www.myfirstbookaboutdna.com My First Book About DNA] Designed for children to learn more about DNA. *[http://www.dnai.org DNA Interactive] (requires Macromedia Flash) *[http://www.fidelitysystems.com/Unlinked_DNA.html DNA under electron microscope] Nucleic acids Genetics DNA ht:ADN la:Acidum deoxyribonucleinicum ms:DNA simple:DNA su:DNA ta:DNA th:ดีเอ็นเอ vi:DNA
''Featured on Template:April 25 selected anniversaries (may be in HTML comment)'' == Archives == * ''/archive 1'' * ''/archive 2'' <= If you want to know why this page was intially protected, read this. * ''/archive 3'' * ''/archive 4'' <= If you want to know why this page is still protected, read this. * ''/archive 5'' <= More about protection unprotection and co. If you want to know about the unprotection of early march * /archive 6 <= About DNA as a disambiguation page * /archive 7 <= Last discussions on the article itself. * ''/archive 8'' <= Personal attacks not relevant to the issue at stake * /archive 9 <= Earlier proposals for intro and discussion * ''/archive 10'' <= Discussion about how to manage the conflict * ''/archive 11'' ==State of affairs 04/29/04== The introductory passage is unnecessarily protected. User:Bensaccount 23:08, 29 Apr 2004 (UTC) List of people currently interested in this page: #User:Bensaccount 23:11, 29 Apr 2004 (UTC) # User:Patrick0Moran 01:00, 30 Apr 2004 (UTC) #User:Stewartadcock 01:10, 30 Apr 2004 (UTC) #User:Peak 04:40, 8 May 2004 (UTC) == Free editing again... == Since it would appear that the main agonists in the prior arguments have left wikipedia (or got bored with this article) I have taken the liberty to remove the HTML comments in the article warning people to not edit the first two paragraphs. I've placed the particular versions into the article which we had an earlier vote on, but these should now be considered by all as open for editting. User:Stewartadcock 22:18, 7 May 2004 (UTC) (If the edit wars start again, then I'll happily slap myself around the face) == Credit due to Franklin. == For the paragraph on credit due to Franklin, see Talk:Rosalind_Franklin. ==DNA for Dummies== Given the fact that DNA and genetic manipulation in general is a hot topic these days, I propose a ''DNA for Dummies'' section in this article, explaining as much as possible of the topic in plain English, for the plain mortal. I know it sounds silly for you scientist types buzzing with controversies around this article, but us plain folk don't quite get the part with "two polynucleotide strands can associate through the hydrophobic effect" for instance, which is part of the "Overview" section in this article. Here's what I managed to learn as a layman mildly interested in the topic, just to get you started with the level of understanding you should assume: :* DNA is made of genes, and genes alone; :* Genes are the organism's cookbook; :* DNA contains genes similarly to binary sequences, in the following way: you can only pair A with T and C with G, no other "atoms" are available, and no other combination works (no need to use the improper term "atom" as I did, I was just trying to convey the Greek meaning of the word for you guys to understand what I mean); :* The order does matter: A+T is not the same with T+A, just as C+G is not the same with G+C; :* However, since there are just four possible combinations, only one element on a conventionally chosen side of the strand is enough to describe the sequence; :* Replication is done not by some magic digital copy machine, but rather by splitting the strand in the middle via relatively trivial chemical reactions, and drowning it in a "gene soup" (yes, I know, faulty layman terms; again, this is why I write this, just to make you see the level of understanding for non-scientist types). Since each of the "atoms" can only combine with a single type of pair, each element in each half-pair will only stick to their predetermined match. This way, each half of the strand ends up as a replica of the original, mutations notwithstanding; :* Mutations are simply chemical imperfections in this process: the chain is trimmed, split or other elements get stuck at the end of it; all other basic mutations can be described as combinations of these accidental "operations". I'm sure that you can describe the whole process better and a lot more accurate than I did above, even in layman's terms, and that's why I didn't write that section myself, although I believe that my general grasp of the phenomenon is reasonably accurate. I think that we're trying to build an encyclopedia "by everyone, for everyone", therefore such a section shouldn't be out of place in this article. Thank you at least for reading all the proposal! --User:Gutza 02:32, 3 Oct 2004 (UTC) Well, one fears that such a section would die the "death by a thousand cuts" that the rest of the article has...nonetheless, hoping you'll have good luck with it, but perhaps I can help you with a formulation that would be less likely to mislead by ''over''-simplification. :* Genes are the organism's cookbook; :* DNA is made of genes, areas that regulate genes, and areas that either have no function, or a function we don't know; :* DNA is organized as two complementary strands, head-to-toe, with bonds between them that can be "unzipped" like a zipper, separating the strands; :* DNA is encoded with four interchangeable "building blocks", called "bases", which can be abbreviated A, T, C, and G; each base "pairs up" with only one other base: A+T, T+A, C+G and G+C; that is, an "A" on one strand of double-stranded DNA will "mate" properly only with a "T" on the other, complementary strand; :* The order does matter: A+T is not the same with T+A, just as C+G is not the same with G+C; :* However, since there are just four possible combinations, naming only one base on the conventionally chosen side of the strand is enough to describe the sequence; :* The order of the bases along the length of the DNA is what it's all about, the sequence itself is the description for genes; :* Replication is done not by some magical copy machine, but rather by splitting (unzipping) the double strand down the middle via relatively trivial chemical reactions, and recreating the "other half" of each new single strand by drowning each half in a "soup" made of the four bases. Since each of the "bases" can only combine with one other base, the base on the old strand dictates which base will be on the new strand. This way, each split half of the strand plus the bases it collects from the soup will ideally end up as a complete replica of the original, unless a mutation occurs; :* Mutations are simply chemical imperfections in this process: a base is accidentally skipped, inserted, or incorrectly copied, or the chain is trimmed, or added to; all other basic mutations can be described as combinations of these accidental "operations". I'm sure this can be improved on, or made clearer. But I'd avoid saying DNA consists only of genes in any case, because it's not true.- User:Nunh-huh 02:52, 3 Oct 2004 (UTC) Thank you for the clarifications! I would really hold on to something along the lines of my "drowning in a gene soup" in the replication part, if that is reasonably accurate, and obviously with rephrasing to convey the proper idea. I think that's a very good visual representation of the "magic" and beauty of the DNA replication process -- the fact that the process is so robust that it allows for reasonably accurate replication without very controlled conditions. Apart from that, I think your version is extremely close to what I had in mind, thank you for the adjustments! I'll wait for revisions here for a couple of more days, and then I'll insert it in the article if nobody else beats me to it. By the way, do you think the section title "DNA for Dummies" would be out of line in this article? --User:Gutza 12:12, 3 Oct 2004 (UTC) Oh, I just realized that we miss the part where we explain the double-strand structure; unfortunately my terminology is so incomplete that I can't even start to explain that part without making a fool of myself. Can you please add another bullet point between the second and the third explaining this? A nucleotide is composed of three parts: 5-phosphate groups, Thank you again! --User:Gutza 12:18, 3 Oct 2004 (UTC) There are no genes in "gene soup": genes are on the DNA. The "soup" as it were includes the four bases, but no genes. Genes are ordered sequences of bases, and a soup is by its very nature unordered. - User:Nunh-huh 20:35, 3 Oct 2004 (UTC) Thank you for the structure bullet point! Regarding the gene soup, this is precisely why I think this section is needed: I was unable to make the clear-cut distinction between genes and bases until you made the point above. I reordered some of the points as to make more sense, included your explanation about the genes and explained the "soup" thing at the replication bullet point. The section "DNA for Dummies" is now complete as far as I am concerned, this is exactly the level of understanding and detail I was going for. Please make any final corrections you feel are required, and tomorrow I'll copy it in the article. Thank you for the patience, I think the result is great - never saw such a great brief and comprehensive explanation of the topic when I was trying to understand it! :-) --User:Gutza 07:38, 4 Oct 2004 (UTC) : I agree -- it would be more accurate to say that DNA is a long chain of "bases" (nucleotides). I like the analogy of ''dunking a strand in a "nucleotide soup" of all 4 kinds of bases.''. --User:DavidCary 02:03, 16 May 2005 (UTC) == Split off the history section == I think this came up a while ago. It was proposed at one point to split off the "The discovery of DNA and the double helix" section into its own article, so that it can be expanded. It is a facinating story, and I'm wondering if we're doing it justice bunched in with the "science" content. Any objections to moving forward with that? Any suggestions for a name of the new page before we do it? I'm partial to something simple like Discovery of DNA. It's a slight misnomer, since the interesting part is the discovery of the helical structure, but a simple title like that has its benefits. -- User:Netoholic User talk:Netoholic 07:03, 2004 Oct 14 (UTC) :I think that would be a good idea; go ahead and do it. I'm not so sure about the title though. Maybe something like Discovery of DNA structure? or, History of DNA research? User:Stewartadcock 16:59, 14 Oct 2004 (UTC) == ''Don't change'' comment == While I see nothing wrong with the ''DNA in brief'' section, I'm afraid I do object to the HTML comment as a matter of principle. Wikipedia is all about anyone being able to change anything they want. When we intimidate people into not making changes with scary comments, it obstructs that. Perhaps better would be a brief reminder that that section is an overview and a reference to a section of the talk page. We all want to preserve content we think is good, but content can always be made better, and if someone makes a bad change and you don't catch it, someone else probably will. User:Dcoetzee 03:19, 12 Nov 2004 (UTC) :Just a very, very late comment by the author of that (old-gone) notification. I wrote it out of fear of the "death by a thousand cuts", as Nunh-huh put it in a previous comment on this very page (at least it was the same page at the time of this writing, might've been archived in a different place by the time you read this.) Now that someone has removed that notification, it looks like my "warning" wasn't really called for, since the "in brief" section still stands, and still matches the original goal. Therefore I salute your pro-wiki attitude, Deco, and I'm mildly ashamed that I felt the need for that warning sign, in the Wikipedia context! :-) --User:Gutza 21:25, 7 May 2005 (UTC) == Other natural information encodings? == Is anyone aware of any other naturally occurring examples of information being encoded and read? Is DNA known to be uniquely suitable for this task, or is it just accidental that the role of encoding information fell to DNA? -- User:RussAbbott :You might find a few other methods in epigenetic inheritance. Also, there are viruses whose genomes are encoded with RNA, but that might not be different enough from DNA to count for your purposes (PNA may also have once been used as a genetic matieral when life first began, but that's just hypothetical. See also Origin of life for some other discussion and possibilities). Prions appear to pass on information about their conformations without DNA being used in the process, but I suspect this might be getting near the fuzzy boundary between information transmission and something simpler like crystal growth. User:Bryan Derksen 08:38, 16 Nov 2004 (UTC) :: I'm really looking for other examples of naturally occurring digitally encoded information that is clearly separated from the medium in which it is encoded. RNA is too much like DNA to be a good example for me. -- User:RussAbbott : Coding, reading, and manufacturing is very much a life process. Bees make their wax combs according to some kind of innate pattern. It is not known whether there is a pattern for combs in the DNA, or in some intermediate structure that is itself produced on the basis of what is encoded in DNA, or whether the hexagonal form may simply the the form that tightly packed cylinders of wax would take, i.e., that the hexagonal shape is not based on an internal plan at all. It is known, however, that bees can be encouraged to make larger or smaller cells by supplying them with flat wax sheets onto which have been imprinted the shapes of the bottoms of cells. If the hexagonal forms imprinted on the wax sheets are smaller/larger, then the cells constructed on them will be smaller/larger. I doubt that there could be anything else on a molecular level -- unless somebody does something in nanotechnology like that. So the only thing you might find would be an animal that carries around a sample of something (a saw, for instance) and uses that sample as a pattern to make another copy. As far as I know, it is considered remarkable for non-humans to use slightly fabricated artifacts as tools. I can't think of any animal that uses a pattern to make something. The earliest instance of the human use of a pattern that I know about appears in the ''Book of Poetry'' (''Shi Jing''). One poem says, "[I] take an ax to go cut an ax handle. Can the pattern [I need] be far from hand?" Humans are part of nature, but I doubt this is really the kind of thing that you want. User:Patrick0Moran 00:38, 17 Nov 2004 (UTC) ::Using a sample is not what I'm after anyway. I'm looking for information encoded and read digitally. --User:RussAbbott 02:29, 17 Nov 2004 (UTC) :::Uh, memory (as in human memory) is stored (human brain and also elsewhere) and read. User:Raul654 02:49, Nov 17, 2004 (UTC) :::Information is stored somewhere, and in some form(s), and this stored information we call memory. And it may get recalled (found) and read when it is needed. But it isn't at all clear that the storage process is done by a series of "on" and "off" states (such as are represented by 1s and 0s in binary numbers), or even 3, 4, ... or some other relatively small number of discernable states. Neurons grow and change their connections during the process of learning, but the information may be stored in some kind of an analog form. (I'm not pretending that I know how that would work any more than I am sure that I know how a binary representation of an elephant would look.) Some people think that long term memories are stored away as molecular configurations, codings analogous to DNA codings. :::A related problem lies in our unclear knowledge of the nature of knowledge. Asserting that the mind creates images of things in the outside world, and that the mind knows the thing by looking at the image of the thing involves us in infinite regress or else in the idea of a little man who lives in our brain and "looks at" the images our brain creates to represent the outside things. But then the question becomes: How does the little man see and understand the images? Does he have a still smaller little man... :::Understanding how single cells identify things on their own scale may be helpful to understanding knowledge and storage of knowledge. I am trusting my memory, so the following account may not be very accurate, but it may be sufficient to get an important idea across: An immune cell in the blood stream may be able to "dock" with a cowpox virus and/or with a smallpox virus. Once it has docked, the immune cell becomes functionally different than when it had a "key" in its "lock." In its new state it signals the body to make antibodies that will fight either cowpox or smallpox viruses. Note that there is not an image of the cowpox virus, but a negative image a "lock" into which the virus (or a significant part of it) will fit. A sucrose molecule will dock with (be recognized by) a sweetness detector, but so will several other molecules, some of which are useful as artificial sweetners. There doesn't seem to me to be a "digital" process going on here. One of the hallmarks of digital memory is that because, e.g., a point on a CD-ROM is either burned or not burned, one can get a very clear record of something and the record will not gradually fade away as will an old color photo. Nor will the image fuzz out to nothing as an analog image will be degraded by a process of copying and recopying. By using a technique called "cyclical redundancy checking" (CRC) it is even possible to check the digital record to see whether a point has gotten burned that was not burned when the record was originally created. So digital records tend to be less smooth. (There is no way of handling a record that really ought to be 1.5. You either write a 1 or you write a 0. It's the difference between a water-color painting and a half-tone screen image where there are colored dots scattered fairly densely over an otherwise colorless page.) But digital records can potentially be preserved forever. All you need to do is make back-up copies to double-check against and periodically copy your old and decaying CDs onto fresh new CDs, and then check them against each other point by point. :::How organisms go from recognizing sugar, salt, etc. in the water they are swimming in to recognizing macro-scale entities visually (or in other ways) is very unclear to me. But some parts of the recognition process appear to have been preserved. Even whales will be identified as fish until the naive observer investigates more closely. Sheep and goats may be identified as "the same kind of animal" by the untutored observer. So on those grounds I'm doubtful about memory being a digital process. Memory has to be a record of an identification or series of identifications, or so it seems to me. :::If memory and learning were digital processes, then each neural connection would either be a 1 or a 0. There would be no stronger connections and no weaker connections unless the relative strengths actually reflected the number of on and off connections involved to make a kind of aggregate connection. But I don't recall every having read of anyone asserting that neural connections are either "totally there" or "totally not there." :::I take it that what you are looking for is a system of recording and reading that depends on a small number of "digits" -- u, v, w, z, for instance, that are ordered into a meaningful sequence so that, let's say, uuxuxvw would mean "hot body core" or something meaningful but simple like that. User:Patrick0Moran 09:53, 17 Nov 2004 (UTC) ::Your last paragraph captures it. The immune system and other forms of key-and-lock recognition are not the same since they are more shape-based than digital. Perhaps one needs shapes to recognize each individual digit. (That's an interesting point.) But I'm looking for an example of what we would consider naturally occurring digital recording other than DNA/RNA. --User:RussAbbott 23:55, 17 Nov 2004 (UTC) ::: The basic distinction you want to make is between forms of recording that are "digital" and forms that are analog. A vinyl phonograph recording is analog. The instantanious variations of air pressure are recorded as instantanious variations of height or width in the groove wall. If you examine the record microscopically you would not see the "stairstep" effect that one gets when one blows up a digital picture (called "aliasing"). Binary digital recordings always are a kind of square wave,i.e., there is either something on the thirteenth step of the ladder or there is not. You can't put half or a third of your weight on a ladder rung in a digital system. So you always "falsify" the data to some extent. If you want to go to a finer "grain" you swap the 100 step ladder for one with 200 rungs, and represent the 13.5 you couldn't get before with 27. In other words, you always deal integer math. ::: How one "reads" the digital record is probably not really relevant to your basic question. One can read a CD-ROM with a microscope if you have to. Somebody with small enough "fingers" could read it like a braille record if the intervening plastic could be removed so you could get your fingers into the pits. ::: The machinery needed to read DNA and to fabricate amino acids on that basis is fantastic. To have a competing system of digital recording, digital reading, and actions programmed on the aforesaid operations would be tantamount to a second form of life since such a "machine" could be augmented to fabricate instances of itself. That is one of the goals of nanotechnology that has at least been talked about. If we wanted to turn an asteroid rich in some valuable ore into neat bricks of the purified metal, one way to do it would presumably be to create nanocritters that would be able to reproduce themselves and would be able to disassemble the oxide of the metal into purified metal and "slag." But we don't know how to do that kind of thing yet. We are just beginning to operate at that size level, and many researchers are looking to world of biology for models of how to do these tasks. ::: One of the forerunners of an early standby of computer interfacing was the punch cards that were used by weaving mills to automatically control the production of complex woven patterns. That is at least of kind of model for the sort of digital data recording you seek. The specific material representations involved don't matter much. Whether it is an IBM punch card or a player piano roll, or a series of bottles and gaps between bottles on top of a wall somewhere, the presence vs. absence relationship can be translated into many forms. So what animal, other than man, arranges things to represent information? Humans who cannot count can keep track of the number of sheep in their flock by putting one stone into a pouch for every sheep let out of the fold in the morning and then checking to see whether, if one stone is removed from the pouch for every sheep that reenters the fold at night, there are any stones left over in the pouch. If there is a stone or two left over, that may mean that the sheep herder needs to go looking for the lost sheep. Do other animals do this kind of thing? Do other primates knot cords? Do elephants dig notches into trees to represent the number of offspring they have given birth to? The closest kind of representation like that lies in the non-linguistic parts of at least some animals. It turns out that crows have better memories than humans. If I recall correctly, if 3 men enter a blind and 2 emerge, the crows are not deceived. Even if 7 enter and 6 emerge, the crow still knows that there is a hunter down there waiting to get him/her. So if you want to fool a crow you have to exceed the buffer capacity of the crow's mind. The memory buffer in the crow's mind/brain is stuffed full at 7. Anything over that just spills over the top. Humans' buffers are generally limited to 5. ::: If I recall correctly, there has been some work done with the memory buffers of honeybees. I'm not sure that a chemical/mechanical/electrical basis for the storage has been identified, but it appears that bees have a relatively small number of individual memory buffers. Bees need to be able to remember things like "compass direction" (actually a measurement based on orienting to direction by observing the polarization of sunlight). Bees are known to report on the presence of nectar and to report on the presence of pollen, so it is likely that there are memory buffers (maybe just yes and no entries) for "nectar?" and "pollen?". I probably read about this stuff in an article in ''Scientific American'' ten or twenty years ago. Is that the kind of thing you want? ::: Any use of symbolic representations by non-humans would be considered a major find, so if there are ants keeping track of the number of ant cows they have by biting gashes in blades of grass or something like that then that fact will get intense attention when it is discovered. ::: A systematic way of investigating this matter would be to ask whether there are non-DNA molecular codes, whether there are digital records kept by single-celled creatures somehow, whether multi-celled creatures (rotifers, for instance) scratch marks or collect markers, etc., etc. If I had to start looking at one point I think I would ask whether birds ever collect stones to represent, e.g., the number of eggs they have laid. (Useful if you think a cowbird might have managed to sneak something into your nest.) ::: It would be interesting to know whether crows remember "7 predators" by writing "1111111" in their predator buffers, or whether they write "111", or, I guess they could just write "7" (in whatever language crows count in). User:Patrick0Moran 06:54, 18 Nov 2004 (UTC) ::: I just remembered: Prairie dogs can identify individual predators, and they communicate such information by a kind of prairie dog language. If they can call out "three wolves" then you've got your digital representation. Then the next interesting question would be how the information is actually stored in their minds/brains... User:Patrick0Moran 07:02, 18 Nov 2004 (UTC) == Verbless sentence == *"Avery the medium of transfer of traits as the transforming principle; his identified DNA as the transforming principle, and not protein as previously thought." Huh? Sentences without verbs cause of confusion for me. — User:Livajo | User talk:Livajo 14:33, 25 Apr 2005 (UTC) ==DNA au Francais== The people at fr have an interesting approach to the organziation of the diaspora of DNA articles and pages. The page in question is at fr: DNA, mRNA, and many others I suppose. It's a big box with the research structure of DNA science organized into all the possible pages. It certainly gets an A for Wikification. It is so easy to use.--User:McDogm 16:13, 7 May 2005 (UTC) == Hash? What has become of this article? == It has been a while since I've looked at this article. It used to make sense to me. Now just looking at it gives me a headache. I see about 50 separate sections each consisting of 3 or 4 lines. I suppose I will have to spend hours with the history of the article to see how it has evolved (?) to its current state, but do others really think this is a desirable configuration? User:Patrick0Moran 06:13, 8 May 2005 (UTC) :I agree with you. User:Gene Nygaard 10:22, 8 May 2005 (UTC) == the name "deoxyribose nucleic acid" vs. "deoxyribonucleic acid" == The article currently inconsistently sometimes uses "deoxyribose nucleic acid" and other times uses "deoxyribonucleic acid". Should the article explicitly mention why one name is preferred over the other ? --User:DavidCary 02:03, 16 May 2005 (UTC) :Yes, if that's the case. But is one preferred over the other? I certainly always use the full term (currently the page title), which I thought this was more common and has always been used in the intro to the page. But according to googlefight ''deoxyribionucleic acid'' is more commonly used by quite a large margin [http://www.googlefight.com/index.php?lang=en_GB&word1=deoxyribose+nucleic+acid&word2=deoxyribonucleic+acid]. It's Wikipedia policy to use consistant spelling, so we need to pick one or the other and standardise the spelling (but still mention alternative spellings). But in the light of the googlefight result I have no idea what to go for. Is there an official body (I asume IUPAC nomenclature is not relevant to biochemistry) that has set a standard? For now we could, wherever possible, use the abbreviation. User:Steinsky User talk:Steinsky 02:31, 16 May 2005 (UTC) ::I checked the genetics and mol bio section of Wikipedia:Library/Science#Biology and found the shorter version to be more common there, too. User:Steinsky User talk:Steinsky 20:27, 23 May 2005 (UTC) :DNA is an abbreviation for Deoxyribose Nucleic Acid. Deoxyribonucleic Acid should point, but to abbreviate this would be DA, not DNA. In any case, I think the abbreviation should point to the full term, and not vice-versa. User:Whig 05:45, 23 May 2005 (UTC) ::However you spell it, there is absolutely no dispute that DNA is its abbreviation. User:Tufflaw 03:32, May 24, 2005 (UTC) ==Page Move== I don't really think that the page move is necessary? What are other peoples opinions?--User:Petaholmes 05:51, 23 May 2005 (UTC) *No, and if the requestor doesn't step forward soon, I'm going to remove the listing. User:Raul654 06:10, May 23, 2005 (UTC) **I didn't nominate it, but I ''think'' the move would conform to Wikipedia:Naming_conventions#Prefer_spelled-out_phrases_to_acronyms, what's your reasoning? --User:Dmcdevit 08:31, 23 May 2005 (UTC) ***I think it should stay since joe public is going to have heard of DNA, but probably not deoxy...... There are several pages that are titled as acronyms that are in a similar situation, H.D. comes to mind, the rule is more so interpreted as use the most common name --User:Petaholmes 08:54, 23 May 2005 (UTC) ****It's more than just the common name though, IMHO. H.D. was her "official" name really, as it was how her work was attributed, similar to how the NAACP and the SAT have articles under those names because their respective organizations have officially declared those letters their official names. Whereas the American Civil Liberties Union and the Tennessee Valley Authority are placed at their spelled out name despite being commonly known by their acronyms. I probably could have thought of better examples, but I think these are good illustrations. Besides, it's not as if there wouldn't be a redirect. --User:Dmcdevit 09:28, 23 May 2005 (UTC) *****I express no opinion on "DNA" versus a correctly spelled-out name, but, to avert any possible mixup, I note that the requested move is to the misspelling Deoxyribionucleic acid (superfluous ''i'' after the ''b''). User:JamesMLane 10:18, 23 May 2005 (UTC) ****Quoting the full text of the Wikipedia:Naming_conventions#Prefer_spelled-out_phrases_to_acronyms: Avoid the use of acronyms in page naming unless the term you are naming is almost exclusively known only by its acronym and is widely known and used in that form (NASA, SETI, and radar are good examples). The page should be called DNA with redirects from the full name (and that misspelling). User:Proto 11:18, 23 May 2005 (UTC) *****I agree completely - the average person looking up this subject in an encyclopedia will look for DNA (I would suggest most often to find out what the acronym actually stands for). It is popularly known by its initials and should remain. User:Tufflaw 13:11, May 23, 2005 (UTC) ******I think I'd prefer the article to stay at DNA. However, if the page ''does'' end up being moved, then DNA should redirect there; it should not be a disambiguation page. Also, should it be moved, the new title should be Deoxyribonucleic acid (no capitalization of "acid". — User:Knowledge Seeker User talk:Knowledge Seeker 20:00, 23 May 2005 (UTC) *******Incidentally, the article begins saying, "Deoxyribose nucleic acid (DNA) is a nucleic acid..." I've always seen it as "deoxyribonucleic acid", not "deoxyribose nucleic acid". All modern biology textbooks, medical textbooks, and journals that I can think of use the former, at least in the United States. ''Merriam-Webster'' also lists "[http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=dna&x=0&y=0 deoxyribonucleic acid]". Is there any source that uses the three-word version? Otherwise I'll change it. — User:Knowledge Seeker User talk:Knowledge Seeker 20:14, 23 May 2005 (UTC) ********Er... see the section above. User:Steinsky User talk:Steinsky 20:20, 23 May 2005 (UTC) User:Violetriga User_talk:violetriga 09:57, 27 May 2005 (UTC) ==the Other DNA== There ought to be a mention of Douglas Noel Adams on the page. User:24.91.43.225 17:26, 10 Jun 2005 (UTC) :There is - the top link goes to the disambiguation page. User:Tufflaw 19:04, Jun 10, 2005 (UTC) ==Cleanup== Ok, so this page has been listed on :Wikipedia:Cleanup. Before attampting any changes I think it would be a good idea to sketch out what the article should look like here. :User:Jerzy listed the page and notes: "oversized article (30K, 11 main hdgs & 19 subordinate ones) should have most main sections reduced to summaries with no subordinate hdgs but links to 'Main articles'". I agree and sugest the following sections, each with its own main article: *''Molecular structure and mechanical properties'' - two subsections / two "main articles". Including information on "Direction of DNA strands". *''DNA fingerprinting'' for crime and for identification of unknown people / parents etc. and also possibly in fiction. *''Replication'' - this has already been done, I think the section needs to be a little longer. *''History of DNA research''. *What I am less sure about is ''The role of the sequence'' - should this be included in a section called, e.g. ''DNA and [the encoding of] genes''? Comments are very welcome! User:Andreww 09:37, 20 Jun 2005 (UTC) P.S. This talk page also needs cleaning up (archiving). I just reverted some changes to the page to make the structure agree with the project science to-do list at the top of the page. Does anybody think this list is a sensible structure for the page? Also, as nobody has complained about my proposed cleanup plan I am going to get started. User:Andreww 08:45, 22 Jun 2005 (UTC) I don't really support moving content out of this article into daughter articles. The disorganised feeling is mainly due to all the==h3== and ====h4==== headings. There should be a section on DNA applications and not where it occurs in the article now, the DNA in brief should be written as prose or deleted all together.--User:Petaholmes 08:53, 22 Jun 2005 (UTC)
:If you are goign to go ahead with breaking the article up the Direction of DNA strands should probably go with the mechanical properties--User:Petaholmes 08:55, 22 Jun 2005 (UTC)
Hi, I feel a bit sad about that revert now that all my work is gone :-/ It was more or less my first 'effort' here in the Wikipedia and maybe I haven't understand the way of working... I thought since there is a to-do list I should follow it to arrange the structure... if not, why is that to-do list there? Who wrote it? I thought it was a group of people after a debate that took part in the past or something like this... or is it neccessary to debate about the structure again? User:Alzhaid 15:53, 22 Jun 2005 (UTC)
Deoxyribonucleic acid (DNA) is a nucleic acid which carries genetics instructions for the developmental biology of all cellular forms of life and many viruses. Nucleic acidsGenetics vi:Category:DNA
#REDIRECTDNA_(disambiguation)
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DNA
:''For other uses, see DNA (disambiguation).'' Deoxyribonucleic acid (DNA) or deoxyribose nucleic acid is a nucleic acid that contains the genetics instructions specifying the developmental biology of all cellular forms of life (and many viruses). DNA is often referred to as the molecule of heredity, as it is responsible for the genetic propagation of most biological inheritance traits. During reproduction, DNA is DNA replication and transmitted to the offspring. In bacterium and other prokaryote biological cell organisms, DNA is not separated from the cytoplasm by a nuclear envelope. In the eukaryote cells that make up plants, animals and in other multi-cellular organisms, by contrast, most of the DNA is located in the cell nucleus. The energy-generating organelles known as chloroplasts and mitochondria also carry DNA, as do many viruses. == DNA in brief == This section presents a brief and simple overview of DNA. * Genes can be loosely viewed as the organism's "cookbook"; * A strand of DNA contains genes, areas that gene regulation, and areas that either have no function, or a function junk DNA; * DNA is organized as two complementary strands, head-to-toe, with bonds between them that can be "unzipped" like a zipper, separating the strands; * DNA is encoded with four interchangeable "building blocks", called "base pair ", which can be abbreviated Adenine, Thymine, Cytosine, and Guanine; each base "pairs up" with only one other base: A+T, T+A, C+G and G+C; that is, an "A" on one strand of double-stranded DNA will "mate" properly only with a "T" on the other, complementary strand; * The order does matter: A+T is not the same as T+A, just as C+G is not the same as G+C; * However, since there are just four possible combinations, naming only one base on the conventionally chosen side of the strand is enough to describe the sequence; * The order of the bases along the length of the DNA is what it's all about, the DNA sequence itself is the description for genes; * DNA replication is performed by splitting (unzipping) the double strand down the middle via relatively trivial chemical reactions, and recreating the "other half" of each new single strand by drowning each half in a "soup" made of the four bases. Since each of the "bases" can only combine with one other base, the base on the old strand dictates which base will be on the new strand. This way, each split half of the strand plus the bases it collects from the soup will ideally end up as a complete replica of the original, unless a mutation occurs; * Mutations are simply chemical imperfections in this process: a base is accidentally skipped, inserted, or incorrectly copied, or the chain is trimmed, or added to; all other basic mutations can be described as combinations of these accidental "operations". ==DNA in crime== Forensic science can use DNA located in blood, semen, or hair left at the scene of a crime to identify a possible suspect, a process called DNA profiling or genetic fingerprinting. In DNA profiling the relative lengths of sections of repetitive DNA, such as short tandem repeats and minisatellites, are compared. DNA profiling was developed in 1984 by English geneticist Alec Jeffries, and was first used in 1986 in the Enderby murders case in Leicestershire, England. Many jurisdictions require convicts of certain types of crimes to provide a sample of DNA for inclusion in a computerized database. This has helped investigators solve old cases where the perpetrator was unknown and only a DNA sample was obtained from the scene (particularly in rape cases between strangers). This method is one of the most reliable techniques for identifying a criminal, but is not always perfect, for example if no DNA can be retrieved, or if the scene is contaminated with the DNA of several possible suspects. == Overview of molecular structure == [[Image:DNA-structure-and-bases.png|right|thumb|Schematic representation of the DNA which illustrates its double helix structure]] Although sometimes called "the molecule of heredity", pieces of DNA as people typically think of them are not single molecules. Rather, they are pairs of molecules, which entwine like vines to form a double helix (see the illustration at the right). Each vine-like molecule is a strand of DNA: a chemically linked chain of nucleotides, each of which consists of a sugar, a phosphate and one of four kinds of nucleobases ("bases"). Because DNA strands are composed of these nucleotide subunits, they are polymers. The diversity of the bases means that there are four kinds of nucleotides, which are commonly referred to by the identity of their bases. These are adenine (A), thymine (T), cytosine (C), and guanine (G). In a DNA double helix, two polynucleotide strands can associate through the hydrophobic effect. Specificity of which strands stay associated is determined by base pair. Each base forms hydrogen bonds readily to only one other -- A to T and C to G -- so that the identity of the base on one strand dictates the strength of the association; the more complementary bases exist, the stronger and longer-lasting the association. The cell's machinery is capable of ''melting'' or disassociating a DNA double helix, and using each DNA strand as a template for synthesizing a new strand which is nearly identical to the previous strand. Errors that occur in the synthesis are known as mutations. The process known as PCR mimics this process in vitro in a nonliving system. Because pairing causes the nucleotide bases to face the helical axis, the sugar and phosphate groups of the nucleotides run along the outside; the two chains they form are sometimes called the "backbones" of the helix. In fact, it is chemical bonds between the phosphates and the sugars that link one nucleotide to the next in the DNA strand. ==The role of the sequence== Within a gene, the sequence of nucleotides along a DNA strand defines a protein, which an organism is liable to manufacture or "gene expression" at one or several points in its life using the information of the sequence. The relationship between the nucleotide sequence and the amino acid sequence of the protein is determined by simple cellular rules of Translation (biology), known collectively as the genetic code. The genetic code is made up of three-letter 'words' (termed a codon) formed from a sequence of three nucleotides (e.g. ACT, CAG, TTT). These codons can then be translated with messenger RNA and then transfer RNA, with a codon corresponding to a particular amino acid. Since there are 64 possible codons, most amino acids have more than one possible codon. There are also three 'stop' or 'nonsense' codons signifying the end of the coding region. In many species of organism, only a small fraction of the total sequence of the genome appears to encode protein. The function of the rest is a matter of speculation. It is known that certain nucleotide sequences specify affinity for DNA binding proteins, which play a wide variety of vital roles, in particular through control of replication and transcription. These sequences are frequently called regulatory sequences, and researchers assume that so far they have identified only a tiny fraction of the total that exist. "Junk DNA" represents sequences that do not yet appear to contain genes or to have a function. Sequence also determines a DNA segment's susceptibility to cleavage by restriction enzymes, the quintessential tools of genetic engineering. The position of cleavage sites throughout an individual's genome determines one kind of an individual's "DNA fingerprinting". ==DNA replication== ''Main article:'' DNA replication DNA replication or DNA synthesis is the process of copying the double-stranded DNA prior to cell division. The two resulting double strands are generally almost perfectly identical, but occasionally errors in replication can result in a less than perfect copy (see mutation), and each of them consists of one original and one newly synthesized strand. This is called ''semiconservative replication''. The process of replication consists of three steps: ''initiation'', ''replication'' and ''termination''. ==Mechanical properties relevant to biology== see Mechanical properties of DNA. ===Strands association and dissociation=== The hydrogen bonds between the strands of the double helix are weak enough that they can be easily separated by enzymes. Enzymes known as helicases unwind the strands to facilitate the advance of sequence-reading enzymes such as DNA polymerase. The unwinding requires that helicases chemically cleave the phosphate backbone of one of the strands so that it can swivel around the other. The strands can also be separated by gentle heating, as used in PCR, provided they have fewer than about 10,000 base pairs (10 kilobase pairs, or 10 kbp). The intertwining of the DNA strands makes long segments difficult to separate. ===Circular DNA=== When the ends of a piece of double-helical DNA are joined so that it forms a circle, as in plasmid DNA, the strands are knot theory knotted. This means they cannot be separated by gentle heating or by any process that does not involve breaking a strand. The task of unknotting topologically linked strands of DNA falls to enzymes known as topoisomerases. Some of these enzymes unknot circular DNA by cleaving two strands so that another double-stranded segment can pass through. Unknotting is required for the replication of circular DNA as well as for various types of recombination in linear DNA. ===Great length versus tiny breadth=== The narrow breadth of the double helix makes it impossible to detect by conventional transmission electron microscope, except by heavy staining. At the same time, the DNA found in many cells can be macroscopic in length -- approximately 5 centimetres long for strands in a human chromosome. Consequently, cells must compact or "package" DNA to carry it within them. This is one of the functions of the chromosomes, which contain spool-like proteins known as histones, around which DNA winds. ===Different helix geometries=== The DNA helix can assume one of three slightly different geometries, of which the "B" form described by James D. Watson and Francis Crick is believed to predominate in cells. It is 2 nanometres wide and extends 3.4 nanometres per 10 Base pair of sequence. This is also the approximate length of sequence in which the double helix makes one complete turn about its axis. This frequency of twist (known as the helical ''pitch'') depends largely on stacking forces that each base exerts on its neighbors in the chain. ====Supercoiled DNA==== The B form of the DNA helix twists 360° per 10.6 bp in the absence of strain. But many molecular biological processes can induce strain. A DNA segment with excess or insufficient helical twisting is referred to, respectively, as positively or negatively "supercoil". DNA ''in vivo'' is typically negatively supercoiled, which facilitates the unwinding of the double-helix required for transcription. ====Conditions for formation of A and Z helices==== The two other known double-helical forms of DNA, called A and Z-DNA, differ modestly in their geometry and dimensions. The A form appears likely to occur only in dehydrated samples of DNA, such as those used in crystallography experiments, and possibly in hybrid pairings of DNA and RNA strands. Segments of DNA that cells have methylation for regulatory purposes may adopt the Z geometry, in which the strands turn about the helical axis like a mirror image of the B form. ====Table of comparison of the properties of different helical forms==== {| border="0" align="center" style="border: 1px solid #999; background-color:#FFFFFF" |-align="center" bgcolor="#CCCCCC" !Geometry attribute !A-form !B-form !Z-form |- |Helix sense ||align="center"| right-handed ||align="center"| right-handed ||align="center"| left-handed |--bgcolor="#EFEFEF" |Repeating unit ||align="right"| 1 bp ||align="right"| 1 bp ||align="right"| 2 bp |----- |Rotation/bp ||align="right"| 33.6° ||align="right"| 35.9° ||align="right"| 60°/2 |--bgcolor="#EFEFEF" |Mean bp/turn ||align="right"| 10.7 ||align="right"| 10.0 ||align="right"| 12 |----- |Inclination of bp to axis ||align="right"| +19° ||align="right"| -1.2° ||align="right"| -9° |--bgcolor="#EFEFEF" |Rise/bp along axis ||align="right"| 0.23 nm ||align="right"| 0.332 nm ||align="right"| 0.38 nm |----- |Pitch/turn of helix ||align="right"| 2.46 nm ||align="right"| 3.32 nm ||align="right"| 4.56 nm |--bgcolor="#EFEFEF" |Mean propeller twist ||align="right"| +18° ||align="right"| +16° ||align="right"| 0° |----- |Glycosyl angle ||align="center"| anti ||align="center"| anti ||align="center"| C: anti,
G: syn |--bgcolor="#EFEFEF" |Sugar pucker ||align="center"| C3'-endo ||align="center"| C2'-endo ||align="center"| C: C2'-endo,
G: C2'-exo |----- |Diameter ||align="right"| 260 nm ||align="right"| 200 nm ||align="right"| 180 nm |--bgcolor="#EFEFEF" |} ===Non-helical forms=== Other, including non-helical, forms of DNA have been described, for example a side-by-side (SBS) configuration. Indeed, it is far from certain that the B-form double helix is the dominant form in living cells. ==Direction of DNA strands== The asymmetric shape and linkage of nucleotides means that a DNA strand always has a discernible orientation or directionality. Because of this directionality, close inspection of a double helix reveals that nucleotides are heading one way along one strand (the "''ascending strand''"), and the other way along the other strand (the "''descending strand''"). This arrangement of the strands is called antiparallel. ===Chemical nomenclature (5' and 3')=== For reasons of chemical nomenclature, people who work with DNA refer to the asymmetric ends of each strand as the '''5%27_end and 3%27_end ends (pronounced \"five prime\" and \"three prime\"). DNA workers and enzymes alike always read nucleotide sequences in the \"5%27_end to 3%27_end direction'''". In a vertically oriented double helix, the 3%27_end strand is said to be ascending while the 5' strand is said to be descending. ===Sense and antisense=== As a result of their antiparallel arrangement and the sequence-reading preferences of enzymes, even if both strands carried identical instead of complementary sequences, cells could properly translate only one of them. The other strand a cell can only read backwards. molecular biology call a sequence "sense" if it is translated or translatable, and they call its complement "antisense". It follows then, somewhat paradoxically, that the template for transcription is the ''antisense'' strand. The resulting transcript is an RNA replica of the ''sense'' strand and is itself ''sense.'' ===An exception: viruses=== Some viruses blur the distinction between sense and antisense, because certain sequences of their genome do double duty, encoding one protein when read 5' to 3' along one strand, and a second protein when read in the opposite direction along the other strand. As a result, the genomes of these viruses are unusually compact for the number of genes they contain, which biologists view as an adaptation (biology). ===As viewed by topologists=== Topologists like to note that the juxtaposition of the 3%27_end end of one DNA strand beside the 5%27_end end of the other at both ends of a double-helical segment makes the arrangement a "crab canon". ==Single-stranded DNA (ssDNA) and repair of mutations== In some viruses DNA appears in a non-helical, single-stranded form. Because many of the DNA repair mechanisms of cells work only on paired bases, viruses that carry single-stranded DNA genomes mutation more frequently than they would otherwise. As a result, such species may adapt more rapidly to avoid extinction. The result would not be so favorable in more complicated and more slowly replicating organisms, however, which may explain why only viruses carry single-stranded DNA. These viruses presumably also benefit from the lower cost of replicating one strand versus two. ==The history of DNA research== [[Image:JamesWatson.jpg|thumb|200px|James D. Watson in the Cavendish Laboratory at the University of Cambridge]] The discovery that DNA was the carrier of genetic information was a process which required many earlier discoveries. The existence of DNA was discovered in the mid 19th century. However, it was only in the early 20th century that researchers began suggesting that it might store genetic information. This was only accepted after the structure of DNA was elucidated by Watson and Crick, which they published in 1953. Watson and Crick proposed the central dogma of molecular biology in 1957, describing the process whereby proteins are produced from cell nucleus DNA. ===First isolation of DNA=== Working in the 19th century, biochemists initially isolated DNA and RNA (mixed together) from cell nuclei. They were relatively quick to appreciate the polymeric nature of their "nucleic acid" isolates, but realized only later that nucleotides were of two types--one containing ribose and the other deoxyribose. It was this subsequent discovery that led to the identification and naming of DNA as a substance distinct from RNA. Friedrich Miescher (1844-1895) discovered a substance he called "nuclein" in 1869. Somewhat later, he isolated a pure sample of the material now known as DNA from the sperm of salmon, and in 1889 his pupil, Richard Altmann, named it "nucleic acid". This substance was found to exist only in the chromosomes. ===Establishing a link between heritable traits and chromosomes=== Max Delbrück, Nikolai V. Timofeeff-Ressovsky, and Karl G. Zimmer published results in 1935 suggesting that chromosomes are very large molecules the structure of which can be changed by treatment with X-rays, and that by so changing their structure it was possible to change the heritable characteristics governed by those chromosomes. (Delbrück and Salvador Luria were awarded the Nobel Prize in 1969 for their work on the genetic structure of viruses.) In 1943, Oswald Theodore Avery discovered that traits proper to the "smooth" form of the ''Pneumococcus'' could be transferred to the "rough" form of the same bacteria merely by making the killed "smooth" (S) form available to the live "rough" (R) form. Quite unexpectedly, the living R ''Pneumococcus'' bacteria were transformed into a new strain of the S form, and the transferred S characteristics turned out to be heritable. Avery called the medium of transfer of traits the transforming principle; he identified DNA as the transforming principle, and not protein as previously thought. In 1953, Alfred Hershey and Martha Chase did an experiment Hershey-Chase experiment that showed, in T2 phage, that DNA is the genetic material (Hershey shared the Nobel prize with Luria). [[Image:FirstSketchOfDNADoubleHelix.jpg|thumb|200px|Francis Crick's first sketch of the deoxyribonucleic acid double-helix pattern]] In 1944, the renowned physicist, Erwin Schrödinger, published a brief book entitled ''What is Life?'', where he maintained that chromosomes contained what he called the "hereditary code-script" of life. He added: "But the term code-script is, of course, too narrow. The chromosome structures are at the same time instrumental in bringing about the development they foreshadow. They are law-code and executive power -- or, to use another simile, they are architect's plan and builder's craft -- in one." He conceived of these dual functional elements as being woven into the molecular structure of chromosomes. By understanding the exact molecular structure of the chromosomes one could hope to understand both the "architect's plan" and also how that plan was carried out through the "builder's craft." Francis Crick, James D. Watson, Maurice Wilkins, Rosalind Franklin, Seymour Benzer, ''et al''., took up the physicist's challenge to work out the structure of the chromosomes and the question of how the segments of the chromosomes that were conceived to relate to specific traits could possibly do their jobs. Just how the presence of specific features in the molecular structure of chromosomes could produce traits and behaviors in living organisms was unimaginable at the time. Because chemical dissection of DNA samples always yielded the same four nucleotides, the chemical composition of DNA appeared simple, perhaps even uniform. Organisms, on the other hand, are fantastically complex individually and widely diverse collectively. Geneticists did not speak of genes as conveyors of "information" in such words, but if they had, they would not have hesitated to quantify the amount of information that genes need to convey as vast. The idea that information might reside in a chemical in the same way that it exists in text--as a finite alphabet of letters arranged in a sequence of unlimited length--had not yet been conceived. It would emerge upon the discovery of DNA's structure, but few researchers imagined that DNA's structure had much to say about genetics. ===Discovery of the structure of DNA=== In the 1950s, only a few groups made it their goal to determine the structure of DNA. These included an American group led by Linus Pauling, and two groups in Britain. At the University of Cambridge, Crick and Watson were building physical models using metal rods and balls, in which they incorporated the known chemical structures of the nucleotides, as well as the known position of the linkages joining one nucleotide to the next along the polymer. At King's College, London, Maurice Wilkins and Rosalind Franklin were examining crystallography patterns of DNA fibers. ====Discovery that DNA is helical==== A key inspiration in the work of all of these teams was the discovery in 1948 by Pauling that many proteins included helical (see alpha helix) shapes. Pauling had deduced this structure from X-ray patterns. Even in the initial crude diffraction data from DNA, it was evident that the structure involved helices. But this insight was only a beginning. There remained the questions of how many strands came together, whether this number was the same for every helix, whether the bases pointed toward the helical axis or away, and ultimately what were the explicit angles and coordinates of all the bonds and atoms. Such questions motivated the modeling efforts of Watson and Crick. ====Discovery that complementary nucleotides occur in equal proportions==== In their modeling, Watson and Crick restricted themselves to what they saw as chemically and biologically reasonable. Still, the breadth of possibilities was very wide. A breakthrough occurred in 1952, when Erwin Chargaff visited Cambridge and inspired Crick with a description of experiments Chargaff had published in 1947. Chargaff had observed that the proportions of the four nucleotides vary between one DNA sample and the next, but that for particular pairs of nucleotides -- adenine and thymine, guanine and cytosine -- the two nucleotides are always present in equal proportions. ====Watson and Crick's model==== [[Image:DNA Model Crick-Watson.jpg|thumb|200px|right|Crick and Watson DNA model built in 1953, currently on display at the National Science Museum in London.]] James Watson and Francis Crick had begun to contemplate double helical arrangements, and they saw that by reversing the directionality of one strand with respect to the other, they could provide an explanation for Chargaff's puzzling finding. This explanation was the complementary pairing of the bases, which also had the effect of ensuring that the distance between the phosphate chains did not vary along a sequence. Watson and Crick were able to discern that this distance was constant and to measure its exact value of 2 nanometres from an X-ray pattern obtained by Franklin. The same pattern also gave them the 3.4 nanometre-per-10 bp "pitch" of the helix. The pair quickly converged upon a model, which they announced before Franklin herself published any of her work. The great assistance Watson and Crick derived from Franklin's data has become a subject of controversy, and it has angered people who believe Franklin has not received the credit due to her. The most controversial aspect is that Franklin's critical X-ray pattern was shown to Watson and Crick without Franklin's knowledge or permission. Wilkins showed it to them at his lab while Franklin was away. ====Publishing of the "Central Dogma"==== Watson and Crick's model attracted great interest immediately upon its presentation. Arriving at their conclusion on February 21 1953, Watson and Crick made their first announcement on February 28. Their paper [http://www.nature.com/genomics/human/watson-crick/ 'A Structure for Deoxyribose Nucleic Acid'] was published on April 25. In an influential presentation in 1957, Crick laid out the "Central Dogma", which foretold the relationship between DNA, RNA, and proteins, and articulated the "sequence hypothesis." A critical confirmation of the replication mechanism that was implied by the double-helical structure followed in 1958 in the form of the Meselson-Stahl experiment. Work by Crick and coworkers deciphered the genetic code not long afterward. These findings represent the birth of molecular biology. James D. Watson, Francis Crick, and Maurice Wilkins were awarded the 1962 Nobel Prize for Medicine for discovering the molecular structure of DNA, by which time Rosalind Franklin had died. Nobel prizes are not awarded posthumously. ==Bibliography== * ''DNA: The Secret of Life'', by James D. Watson. ISBN 0-375-41546-7 ==External links== *[http://nist.rcsb.org/pdb/molecules/pdb23_1.html DNA: PDB molecule of the month] * *[http://www.rotten.com/library/medicine/dna/ Rotten Library] Article on DNA *[http://news.bbc.co.uk/1/hi/sci/tech/2949629.stm 17 April, 2003, BBC News: Most ancient DNA ever?] *Watson, James, and Francis Crick, "''[http://biocrs.biomed.brown.edu/Books/Chapters/Ch%208/DH-Paper.html Molecular structure of nucleic acids], A structure for Deoxyribose Nucleic Acid''". April 2, 1953. (paper on the structure of DNA) *[http://www.myfirstbookaboutdna.com My First Book About DNA] Designed for children to learn more about DNA. *[http://www.dnai.org DNA Interactive] (requires Macromedia Flash) *[http://www.fidelitysystems.com/Unlinked_DNA.html DNA under electron microscope] Nucleic acids Genetics DNA ht:ADN la:Acidum deoxyribonucleinicum ms:DNA simple:DNA su:DNA ta:DNA th:ดีเอ็นเอ vi:DNA
DNA
''Featured on Template:April 25 selected anniversaries (may be in HTML comment)'' == Archives == * ''/archive 1'' * ''/archive 2'' <= If you want to know why this page was intially protected, read this. * ''/archive 3'' * ''/archive 4'' <= If you want to know why this page is still protected, read this. * ''/archive 5'' <= More about protection unprotection and co. If you want to know about the unprotection of early march * /archive 6 <= About DNA as a disambiguation page * /archive 7 <= Last discussions on the article itself. * ''/archive 8'' <= Personal attacks not relevant to the issue at stake * /archive 9 <= Earlier proposals for intro and discussion * ''/archive 10'' <= Discussion about how to manage the conflict * ''/archive 11'' ==State of affairs 04/29/04== The introductory passage is unnecessarily protected. User:Bensaccount 23:08, 29 Apr 2004 (UTC) List of people currently interested in this page: #User:Bensaccount 23:11, 29 Apr 2004 (UTC) # User:Patrick0Moran 01:00, 30 Apr 2004 (UTC) #User:Stewartadcock 01:10, 30 Apr 2004 (UTC) #User:Peak 04:40, 8 May 2004 (UTC) == Free editing again... == Since it would appear that the main agonists in the prior arguments have left wikipedia (or got bored with this article) I have taken the liberty to remove the HTML comments in the article warning people to not edit the first two paragraphs. I've placed the particular versions into the article which we had an earlier vote on, but these should now be considered by all as open for editting. User:Stewartadcock 22:18, 7 May 2004 (UTC) (If the edit wars start again, then I'll happily slap myself around the face) == Credit due to Franklin. == For the paragraph on credit due to Franklin, see Talk:Rosalind_Franklin. ==DNA for Dummies== Given the fact that DNA and genetic manipulation in general is a hot topic these days, I propose a ''DNA for Dummies'' section in this article, explaining as much as possible of the topic in plain English, for the plain mortal. I know it sounds silly for you scientist types buzzing with controversies around this article, but us plain folk don't quite get the part with "two polynucleotide strands can associate through the hydrophobic effect" for instance, which is part of the "Overview" section in this article. Here's what I managed to learn as a layman mildly interested in the topic, just to get you started with the level of understanding you should assume: :* DNA is made of genes, and genes alone; :* Genes are the organism's cookbook; :* DNA contains genes similarly to binary sequences, in the following way: you can only pair A with T and C with G, no other "atoms" are available, and no other combination works (no need to use the improper term "atom" as I did, I was just trying to convey the Greek meaning of the word for you guys to understand what I mean); :* The order does matter: A+T is not the same with T+A, just as C+G is not the same with G+C; :* However, since there are just four possible combinations, only one element on a conventionally chosen side of the strand is enough to describe the sequence; :* Replication is done not by some magic digital copy machine, but rather by splitting the strand in the middle via relatively trivial chemical reactions, and drowning it in a "gene soup" (yes, I know, faulty layman terms; again, this is why I write this, just to make you see the level of understanding for non-scientist types). Since each of the "atoms" can only combine with a single type of pair, each element in each half-pair will only stick to their predetermined match. This way, each half of the strand ends up as a replica of the original, mutations notwithstanding; :* Mutations are simply chemical imperfections in this process: the chain is trimmed, split or other elements get stuck at the end of it; all other basic mutations can be described as combinations of these accidental "operations". I'm sure that you can describe the whole process better and a lot more accurate than I did above, even in layman's terms, and that's why I didn't write that section myself, although I believe that my general grasp of the phenomenon is reasonably accurate. I think that we're trying to build an encyclopedia "by everyone, for everyone", therefore such a section shouldn't be out of place in this article. Thank you at least for reading all the proposal! --User:Gutza 02:32, 3 Oct 2004 (UTC) Well, one fears that such a section would die the "death by a thousand cuts" that the rest of the article has...nonetheless, hoping you'll have good luck with it, but perhaps I can help you with a formulation that would be less likely to mislead by ''over''-simplification. :* Genes are the organism's cookbook; :* DNA is made of genes, areas that regulate genes, and areas that either have no function, or a function we don't know; :* DNA is organized as two complementary strands, head-to-toe, with bonds between them that can be "unzipped" like a zipper, separating the strands; :* DNA is encoded with four interchangeable "building blocks", called "bases", which can be abbreviated A, T, C, and G; each base "pairs up" with only one other base: A+T, T+A, C+G and G+C; that is, an "A" on one strand of double-stranded DNA will "mate" properly only with a "T" on the other, complementary strand; :* The order does matter: A+T is not the same with T+A, just as C+G is not the same with G+C; :* However, since there are just four possible combinations, naming only one base on the conventionally chosen side of the strand is enough to describe the sequence; :* The order of the bases along the length of the DNA is what it's all about, the sequence itself is the description for genes; :* Replication is done not by some magical copy machine, but rather by splitting (unzipping) the double strand down the middle via relatively trivial chemical reactions, and recreating the "other half" of each new single strand by drowning each half in a "soup" made of the four bases. Since each of the "bases" can only combine with one other base, the base on the old strand dictates which base will be on the new strand. This way, each split half of the strand plus the bases it collects from the soup will ideally end up as a complete replica of the original, unless a mutation occurs; :* Mutations are simply chemical imperfections in this process: a base is accidentally skipped, inserted, or incorrectly copied, or the chain is trimmed, or added to; all other basic mutations can be described as combinations of these accidental "operations". I'm sure this can be improved on, or made clearer. But I'd avoid saying DNA consists only of genes in any case, because it's not true.- User:Nunh-huh 02:52, 3 Oct 2004 (UTC) Thank you for the clarifications! I would really hold on to something along the lines of my "drowning in a gene soup" in the replication part, if that is reasonably accurate, and obviously with rephrasing to convey the proper idea. I think that's a very good visual representation of the "magic" and beauty of the DNA replication process -- the fact that the process is so robust that it allows for reasonably accurate replication without very controlled conditions. Apart from that, I think your version is extremely close to what I had in mind, thank you for the adjustments! I'll wait for revisions here for a couple of more days, and then I'll insert it in the article if nobody else beats me to it. By the way, do you think the section title "DNA for Dummies" would be out of line in this article? --User:Gutza 12:12, 3 Oct 2004 (UTC) Oh, I just realized that we miss the part where we explain the double-strand structure; unfortunately my terminology is so incomplete that I can't even start to explain that part without making a fool of myself. Can you please add another bullet point between the second and the third explaining this? A nucleotide is composed of three parts: 5-phosphate groups, Thank you again! --User:Gutza 12:18, 3 Oct 2004 (UTC) There are no genes in "gene soup": genes are on the DNA. The "soup" as it were includes the four bases, but no genes. Genes are ordered sequences of bases, and a soup is by its very nature unordered. - User:Nunh-huh 20:35, 3 Oct 2004 (UTC) Thank you for the structure bullet point! Regarding the gene soup, this is precisely why I think this section is needed: I was unable to make the clear-cut distinction between genes and bases until you made the point above. I reordered some of the points as to make more sense, included your explanation about the genes and explained the "soup" thing at the replication bullet point. The section "DNA for Dummies" is now complete as far as I am concerned, this is exactly the level of understanding and detail I was going for. Please make any final corrections you feel are required, and tomorrow I'll copy it in the article. Thank you for the patience, I think the result is great - never saw such a great brief and comprehensive explanation of the topic when I was trying to understand it! :-) --User:Gutza 07:38, 4 Oct 2004 (UTC) : I agree -- it would be more accurate to say that DNA is a long chain of "bases" (nucleotides). I like the analogy of ''dunking a strand in a "nucleotide soup" of all 4 kinds of bases.''. --User:DavidCary 02:03, 16 May 2005 (UTC) == Split off the history section == I think this came up a while ago. It was proposed at one point to split off the "The discovery of DNA and the double helix" section into its own article, so that it can be expanded. It is a facinating story, and I'm wondering if we're doing it justice bunched in with the "science" content. Any objections to moving forward with that? Any suggestions for a name of the new page before we do it? I'm partial to something simple like Discovery of DNA. It's a slight misnomer, since the interesting part is the discovery of the helical structure, but a simple title like that has its benefits. -- User:Netoholic User talk:Netoholic 07:03, 2004 Oct 14 (UTC) :I think that would be a good idea; go ahead and do it. I'm not so sure about the title though. Maybe something like Discovery of DNA structure? or, History of DNA research? User:Stewartadcock 16:59, 14 Oct 2004 (UTC) == ''Don't change'' comment == While I see nothing wrong with the ''DNA in brief'' section, I'm afraid I do object to the HTML comment as a matter of principle. Wikipedia is all about anyone being able to change anything they want. When we intimidate people into not making changes with scary comments, it obstructs that. Perhaps better would be a brief reminder that that section is an overview and a reference to a section of the talk page. We all want to preserve content we think is good, but content can always be made better, and if someone makes a bad change and you don't catch it, someone else probably will. User:Dcoetzee 03:19, 12 Nov 2004 (UTC) :Just a very, very late comment by the author of that (old-gone) notification. I wrote it out of fear of the "death by a thousand cuts", as Nunh-huh put it in a previous comment on this very page (at least it was the same page at the time of this writing, might've been archived in a different place by the time you read this.) Now that someone has removed that notification, it looks like my "warning" wasn't really called for, since the "in brief" section still stands, and still matches the original goal. Therefore I salute your pro-wiki attitude, Deco, and I'm mildly ashamed that I felt the need for that warning sign, in the Wikipedia context! :-) --User:Gutza 21:25, 7 May 2005 (UTC) == Other natural information encodings? == Is anyone aware of any other naturally occurring examples of information being encoded and read? Is DNA known to be uniquely suitable for this task, or is it just accidental that the role of encoding information fell to DNA? -- User:RussAbbott :You might find a few other methods in epigenetic inheritance. Also, there are viruses whose genomes are encoded with RNA, but that might not be different enough from DNA to count for your purposes (PNA may also have once been used as a genetic matieral when life first began, but that's just hypothetical. See also Origin of life for some other discussion and possibilities). Prions appear to pass on information about their conformations without DNA being used in the process, but I suspect this might be getting near the fuzzy boundary between information transmission and something simpler like crystal growth. User:Bryan Derksen 08:38, 16 Nov 2004 (UTC) :: I'm really looking for other examples of naturally occurring digitally encoded information that is clearly separated from the medium in which it is encoded. RNA is too much like DNA to be a good example for me. -- User:RussAbbott : Coding, reading, and manufacturing is very much a life process. Bees make their wax combs according to some kind of innate pattern. It is not known whether there is a pattern for combs in the DNA, or in some intermediate structure that is itself produced on the basis of what is encoded in DNA, or whether the hexagonal form may simply the the form that tightly packed cylinders of wax would take, i.e., that the hexagonal shape is not based on an internal plan at all. It is known, however, that bees can be encouraged to make larger or smaller cells by supplying them with flat wax sheets onto which have been imprinted the shapes of the bottoms of cells. If the hexagonal forms imprinted on the wax sheets are smaller/larger, then the cells constructed on them will be smaller/larger. I doubt that there could be anything else on a molecular level -- unless somebody does something in nanotechnology like that. So the only thing you might find would be an animal that carries around a sample of something (a saw, for instance) and uses that sample as a pattern to make another copy. As far as I know, it is considered remarkable for non-humans to use slightly fabricated artifacts as tools. I can't think of any animal that uses a pattern to make something. The earliest instance of the human use of a pattern that I know about appears in the ''Book of Poetry'' (''Shi Jing''). One poem says, "[I] take an ax to go cut an ax handle. Can the pattern [I need] be far from hand?" Humans are part of nature, but I doubt this is really the kind of thing that you want. User:Patrick0Moran 00:38, 17 Nov 2004 (UTC) ::Using a sample is not what I'm after anyway. I'm looking for information encoded and read digitally. --User:RussAbbott 02:29, 17 Nov 2004 (UTC) :::Uh, memory (as in human memory) is stored (human brain and also elsewhere) and read. User:Raul654 02:49, Nov 17, 2004 (UTC) :::Information is stored somewhere, and in some form(s), and this stored information we call memory. And it may get recalled (found) and read when it is needed. But it isn't at all clear that the storage process is done by a series of "on" and "off" states (such as are represented by 1s and 0s in binary numbers), or even 3, 4, ... or some other relatively small number of discernable states. Neurons grow and change their connections during the process of learning, but the information may be stored in some kind of an analog form. (I'm not pretending that I know how that would work any more than I am sure that I know how a binary representation of an elephant would look.) Some people think that long term memories are stored away as molecular configurations, codings analogous to DNA codings. :::A related problem lies in our unclear knowledge of the nature of knowledge. Asserting that the mind creates images of things in the outside world, and that the mind knows the thing by looking at the image of the thing involves us in infinite regress or else in the idea of a little man who lives in our brain and "looks at" the images our brain creates to represent the outside things. But then the question becomes: How does the little man see and understand the images? Does he have a still smaller little man... :::Understanding how single cells identify things on their own scale may be helpful to understanding knowledge and storage of knowledge. I am trusting my memory, so the following account may not be very accurate, but it may be sufficient to get an important idea across: An immune cell in the blood stream may be able to "dock" with a cowpox virus and/or with a smallpox virus. Once it has docked, the immune cell becomes functionally different than when it had a "key" in its "lock." In its new state it signals the body to make antibodies that will fight either cowpox or smallpox viruses. Note that there is not an image of the cowpox virus, but a negative image a "lock" into which the virus (or a significant part of it) will fit. A sucrose molecule will dock with (be recognized by) a sweetness detector, but so will several other molecules, some of which are useful as artificial sweetners. There doesn't seem to me to be a "digital" process going on here. One of the hallmarks of digital memory is that because, e.g., a point on a CD-ROM is either burned or not burned, one can get a very clear record of something and the record will not gradually fade away as will an old color photo. Nor will the image fuzz out to nothing as an analog image will be degraded by a process of copying and recopying. By using a technique called "cyclical redundancy checking" (CRC) it is even possible to check the digital record to see whether a point has gotten burned that was not burned when the record was originally created. So digital records tend to be less smooth. (There is no way of handling a record that really ought to be 1.5. You either write a 1 or you write a 0. It's the difference between a water-color painting and a half-tone screen image where there are colored dots scattered fairly densely over an otherwise colorless page.) But digital records can potentially be preserved forever. All you need to do is make back-up copies to double-check against and periodically copy your old and decaying CDs onto fresh new CDs, and then check them against each other point by point. :::How organisms go from recognizing sugar, salt, etc. in the water they are swimming in to recognizing macro-scale entities visually (or in other ways) is very unclear to me. But some parts of the recognition process appear to have been preserved. Even whales will be identified as fish until the naive observer investigates more closely. Sheep and goats may be identified as "the same kind of animal" by the untutored observer. So on those grounds I'm doubtful about memory being a digital process. Memory has to be a record of an identification or series of identifications, or so it seems to me. :::If memory and learning were digital processes, then each neural connection would either be a 1 or a 0. There would be no stronger connections and no weaker connections unless the relative strengths actually reflected the number of on and off connections involved to make a kind of aggregate connection. But I don't recall every having read of anyone asserting that neural connections are either "totally there" or "totally not there." :::I take it that what you are looking for is a system of recording and reading that depends on a small number of "digits" -- u, v, w, z, for instance, that are ordered into a meaningful sequence so that, let's say, uuxuxvw would mean "hot body core" or something meaningful but simple like that. User:Patrick0Moran 09:53, 17 Nov 2004 (UTC) ::Your last paragraph captures it. The immune system and other forms of key-and-lock recognition are not the same since they are more shape-based than digital. Perhaps one needs shapes to recognize each individual digit. (That's an interesting point.) But I'm looking for an example of what we would consider naturally occurring digital recording other than DNA/RNA. --User:RussAbbott 23:55, 17 Nov 2004 (UTC) ::: The basic distinction you want to make is between forms of recording that are "digital" and forms that are analog. A vinyl phonograph recording is analog. The instantanious variations of air pressure are recorded as instantanious variations of height or width in the groove wall. If you examine the record microscopically you would not see the "stairstep" effect that one gets when one blows up a digital picture (called "aliasing"). Binary digital recordings always are a kind of square wave,i.e., there is either something on the thirteenth step of the ladder or there is not. You can't put half or a third of your weight on a ladder rung in a digital system. So you always "falsify" the data to some extent. If you want to go to a finer "grain" you swap the 100 step ladder for one with 200 rungs, and represent the 13.5 you couldn't get before with 27. In other words, you always deal integer math. ::: How one "reads" the digital record is probably not really relevant to your basic question. One can read a CD-ROM with a microscope if you have to. Somebody with small enough "fingers" could read it like a braille record if the intervening plastic could be removed so you could get your fingers into the pits. ::: The machinery needed to read DNA and to fabricate amino acids on that basis is fantastic. To have a competing system of digital recording, digital reading, and actions programmed on the aforesaid operations would be tantamount to a second form of life since such a "machine" could be augmented to fabricate instances of itself. That is one of the goals of nanotechnology that has at least been talked about. If we wanted to turn an asteroid rich in some valuable ore into neat bricks of the purified metal, one way to do it would presumably be to create nanocritters that would be able to reproduce themselves and would be able to disassemble the oxide of the metal into purified metal and "slag." But we don't know how to do that kind of thing yet. We are just beginning to operate at that size level, and many researchers are looking to world of biology for models of how to do these tasks. ::: One of the forerunners of an early standby of computer interfacing was the punch cards that were used by weaving mills to automatically control the production of complex woven patterns. That is at least of kind of model for the sort of digital data recording you seek. The specific material representations involved don't matter much. Whether it is an IBM punch card or a player piano roll, or a series of bottles and gaps between bottles on top of a wall somewhere, the presence vs. absence relationship can be translated into many forms. So what animal, other than man, arranges things to represent information? Humans who cannot count can keep track of the number of sheep in their flock by putting one stone into a pouch for every sheep let out of the fold in the morning and then checking to see whether, if one stone is removed from the pouch for every sheep that reenters the fold at night, there are any stones left over in the pouch. If there is a stone or two left over, that may mean that the sheep herder needs to go looking for the lost sheep. Do other animals do this kind of thing? Do other primates knot cords? Do elephants dig notches into trees to represent the number of offspring they have given birth to? The closest kind of representation like that lies in the non-linguistic parts of at least some animals. It turns out that crows have better memories than humans. If I recall correctly, if 3 men enter a blind and 2 emerge, the crows are not deceived. Even if 7 enter and 6 emerge, the crow still knows that there is a hunter down there waiting to get him/her. So if you want to fool a crow you have to exceed the buffer capacity of the crow's mind. The memory buffer in the crow's mind/brain is stuffed full at 7. Anything over that just spills over the top. Humans' buffers are generally limited to 5. ::: If I recall correctly, there has been some work done with the memory buffers of honeybees. I'm not sure that a chemical/mechanical/electrical basis for the storage has been identified, but it appears that bees have a relatively small number of individual memory buffers. Bees need to be able to remember things like "compass direction" (actually a measurement based on orienting to direction by observing the polarization of sunlight). Bees are known to report on the presence of nectar and to report on the presence of pollen, so it is likely that there are memory buffers (maybe just yes and no entries) for "nectar?" and "pollen?". I probably read about this stuff in an article in ''Scientific American'' ten or twenty years ago. Is that the kind of thing you want? ::: Any use of symbolic representations by non-humans would be considered a major find, so if there are ants keeping track of the number of ant cows they have by biting gashes in blades of grass or something like that then that fact will get intense attention when it is discovered. ::: A systematic way of investigating this matter would be to ask whether there are non-DNA molecular codes, whether there are digital records kept by single-celled creatures somehow, whether multi-celled creatures (rotifers, for instance) scratch marks or collect markers, etc., etc. If I had to start looking at one point I think I would ask whether birds ever collect stones to represent, e.g., the number of eggs they have laid. (Useful if you think a cowbird might have managed to sneak something into your nest.) ::: It would be interesting to know whether crows remember "7 predators" by writing "1111111" in their predator buffers, or whether they write "111", or, I guess they could just write "7" (in whatever language crows count in). User:Patrick0Moran 06:54, 18 Nov 2004 (UTC) ::: I just remembered: Prairie dogs can identify individual predators, and they communicate such information by a kind of prairie dog language. If they can call out "three wolves" then you've got your digital representation. Then the next interesting question would be how the information is actually stored in their minds/brains... User:Patrick0Moran 07:02, 18 Nov 2004 (UTC) == Verbless sentence == *"Avery the medium of transfer of traits as the transforming principle; his identified DNA as the transforming principle, and not protein as previously thought." Huh? Sentences without verbs cause of confusion for me. — User:Livajo | User talk:Livajo 14:33, 25 Apr 2005 (UTC) ==DNA au Francais== The people at fr have an interesting approach to the organziation of the diaspora of DNA articles and pages. The page in question is at fr: DNA, mRNA, and many others I suppose. It's a big box with the research structure of DNA science organized into all the possible pages. It certainly gets an A for Wikification. It is so easy to use.--User:McDogm 16:13, 7 May 2005 (UTC) == Hash? What has become of this article? == It has been a while since I've looked at this article. It used to make sense to me. Now just looking at it gives me a headache. I see about 50 separate sections each consisting of 3 or 4 lines. I suppose I will have to spend hours with the history of the article to see how it has evolved (?) to its current state, but do others really think this is a desirable configuration? User:Patrick0Moran 06:13, 8 May 2005 (UTC) :I agree with you. User:Gene Nygaard 10:22, 8 May 2005 (UTC) == the name "deoxyribose nucleic acid" vs. "deoxyribonucleic acid" == The article currently inconsistently sometimes uses "deoxyribose nucleic acid" and other times uses "deoxyribonucleic acid". Should the article explicitly mention why one name is preferred over the other ? --User:DavidCary 02:03, 16 May 2005 (UTC) :Yes, if that's the case. But is one preferred over the other? I certainly always use the full term (currently the page title), which I thought this was more common and has always been used in the intro to the page. But according to googlefight ''deoxyribionucleic acid'' is more commonly used by quite a large margin [http://www.googlefight.com/index.php?lang=en_GB&word1=deoxyribose+nucleic+acid&word2=deoxyribonucleic+acid]. It's Wikipedia policy to use consistant spelling, so we need to pick one or the other and standardise the spelling (but still mention alternative spellings). But in the light of the googlefight result I have no idea what to go for. Is there an official body (I asume IUPAC nomenclature is not relevant to biochemistry) that has set a standard? For now we could, wherever possible, use the abbreviation. User:Steinsky User talk:Steinsky 02:31, 16 May 2005 (UTC) ::I checked the genetics and mol bio section of Wikipedia:Library/Science#Biology and found the shorter version to be more common there, too. User:Steinsky User talk:Steinsky 20:27, 23 May 2005 (UTC) :DNA is an abbreviation for Deoxyribose Nucleic Acid. Deoxyribonucleic Acid should point, but to abbreviate this would be DA, not DNA. In any case, I think the abbreviation should point to the full term, and not vice-versa. User:Whig 05:45, 23 May 2005 (UTC) ::However you spell it, there is absolutely no dispute that DNA is its abbreviation. User:Tufflaw 03:32, May 24, 2005 (UTC) ==Page Move== I don't really think that the page move is necessary? What are other peoples opinions?--User:Petaholmes 05:51, 23 May 2005 (UTC) *No, and if the requestor doesn't step forward soon, I'm going to remove the listing. User:Raul654 06:10, May 23, 2005 (UTC) **I didn't nominate it, but I ''think'' the move would conform to Wikipedia:Naming_conventions#Prefer_spelled-out_phrases_to_acronyms, what's your reasoning? --User:Dmcdevit 08:31, 23 May 2005 (UTC) ***I think it should stay since joe public is going to have heard of DNA, but probably not deoxy...... There are several pages that are titled as acronyms that are in a similar situation, H.D. comes to mind, the rule is more so interpreted as use the most common name --User:Petaholmes 08:54, 23 May 2005 (UTC) ****It's more than just the common name though, IMHO. H.D. was her "official" name really, as it was how her work was attributed, similar to how the NAACP and the SAT have articles under those names because their respective organizations have officially declared those letters their official names. Whereas the American Civil Liberties Union and the Tennessee Valley Authority are placed at their spelled out name despite being commonly known by their acronyms. I probably could have thought of better examples, but I think these are good illustrations. Besides, it's not as if there wouldn't be a redirect. --User:Dmcdevit 09:28, 23 May 2005 (UTC) *****I express no opinion on "DNA" versus a correctly spelled-out name, but, to avert any possible mixup, I note that the requested move is to the misspelling Deoxyribionucleic acid (superfluous ''i'' after the ''b''). User:JamesMLane 10:18, 23 May 2005 (UTC) ****Quoting the full text of the Wikipedia:Naming_conventions#Prefer_spelled-out_phrases_to_acronyms: Avoid the use of acronyms in page naming unless the term you are naming is almost exclusively known only by its acronym and is widely known and used in that form (NASA, SETI, and radar are good examples). The page should be called DNA with redirects from the full name (and that misspelling). User:Proto 11:18, 23 May 2005 (UTC) *****I agree completely - the average person looking up this subject in an encyclopedia will look for DNA (I would suggest most often to find out what the acronym actually stands for). It is popularly known by its initials and should remain. User:Tufflaw 13:11, May 23, 2005 (UTC) ******I think I'd prefer the article to stay at DNA. However, if the page ''does'' end up being moved, then DNA should redirect there; it should not be a disambiguation page. Also, should it be moved, the new title should be Deoxyribonucleic acid (no capitalization of "acid". — User:Knowledge Seeker User talk:Knowledge Seeker 20:00, 23 May 2005 (UTC) *******Incidentally, the article begins saying, "Deoxyribose nucleic acid (DNA) is a nucleic acid..." I've always seen it as "deoxyribonucleic acid", not "deoxyribose nucleic acid". All modern biology textbooks, medical textbooks, and journals that I can think of use the former, at least in the United States. ''Merriam-Webster'' also lists "[http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=dna&x=0&y=0 deoxyribonucleic acid]". Is there any source that uses the three-word version? Otherwise I'll change it. — User:Knowledge Seeker User talk:Knowledge Seeker 20:14, 23 May 2005 (UTC) ********Er... see the section above. User:Steinsky User talk:Steinsky 20:20, 23 May 2005 (UTC) User:Violetriga User_talk:violetriga 09:57, 27 May 2005 (UTC) ==the Other DNA== There ought to be a mention of Douglas Noel Adams on the page. User:24.91.43.225 17:26, 10 Jun 2005 (UTC) :There is - the top link goes to the disambiguation page. User:Tufflaw 19:04, Jun 10, 2005 (UTC) ==Cleanup== Ok, so this page has been listed on :Wikipedia:Cleanup. Before attampting any changes I think it would be a good idea to sketch out what the article should look like here. :User:Jerzy listed the page and notes: "oversized article (30K, 11 main hdgs & 19 subordinate ones) should have most main sections reduced to summaries with no subordinate hdgs but links to 'Main articles'". I agree and sugest the following sections, each with its own main article: *''Molecular structure and mechanical properties'' - two subsections / two "main articles". Including information on "Direction of DNA strands". *''DNA fingerprinting'' for crime and for identification of unknown people / parents etc. and also possibly in fiction. *''Replication'' - this has already been done, I think the section needs to be a little longer. *''History of DNA research''. *What I am less sure about is ''The role of the sequence'' - should this be included in a section called, e.g. ''DNA and [the encoding of] genes''? Comments are very welcome! User:Andreww 09:37, 20 Jun 2005 (UTC) P.S. This talk page also needs cleaning up (archiving). I just reverted some changes to the page to make the structure agree with the project science to-do list at the top of the page. Does anybody think this list is a sensible structure for the page? Also, as nobody has complained about my proposed cleanup plan I am going to get started. User:Andreww 08:45, 22 Jun 2005 (UTC) I don't really support moving content out of this article into daughter articles. The disorganised feeling is mainly due to all the
DNA
Deoxyribonucleic acid (DNA) is a nucleic acid which carries genetics instructions for the developmental biology of all cellular forms of life and many viruses. Nucleic acidsGenetics vi:Category:DNA
Dna
#REDIRECTDNA_(disambiguation)
Dna
See other meanings of words starting from letter:
D
DA | DB | DC | DE | DF | DG | DH | DI | DJ | DK | DL | DM | DN | DO | DP | DR | DS | DT | DU | DW | DX | DY | DZ |Words begining with Dna:
DNA
DNA
DNA
Dna
Dna
DNA-binding_protein
DNA-DNA_hybridisation
DNA-DNA_hybridisation
DNA-DNA_hybridization
DNA/acrhive_2
DNA/archive_1
DNA/archive_10
DNA/archive_11
DNA/archive_2
DNA/archive_3
DNA/archive_4
DNA/archive_5
DNA/archive_6
DNA/archive_7
DNA/archive_8
DNA/archive_9
DNA/arhive_2
DNA/to_do
DNA/vote
DNA2
DnaA
DNAase_footprinting_assay
DnaB
DNABeast
DnaB_helicase
DnaC
DnaC
DnaC/Delete
Dnadog
DnaG
Dnagod
Dnagod
DnaK
Dnalor
DnAnalytics
Dnanalytics
DNAngel
DnaQ
Dnaquin
DNase
DNase_footprinting
DNase_footprinting_assay
Dnase_footprinting_assay
DNase_I
DNA_(band)
DNA_(band)
DNA_(disambiguation)
DNA_analysis
Dna_array
DNA_Barcode
DNA_barcode
DNA_binding_protein
DNA_Chip
DNA_chip
DNA_computer
DNA_computing
DNA_computing
Dna_computing
DNA_construct
DNA_damage
DNA_EDIT_WAR
DNA_electrophoresis
DNA_electrophoresis
DNA_Extraction
DNA_Extraction
DNA_extraction
DNA_extraction
DNA_fingerprint
DNA_fingerprinting
DNA_fragmentation
DNA_GENETIC_GEAR_METAL
DNA_glycosylase
DNA_glycosylase
DNA_gyrase
DNA_helicase
DNA_holoenzyme
DNA_intercalation.jpeg
DNA_ladder
DNA_ligase
DNA_Lounge
DNA_Lounge
DNA_methylation
DNA_methyltransferase
DNA_Microarray
DNA_microarray
DNA_microarray
DNA_microarrays
DNA_motif
DNA_Pokémon
DNA_Polymerase
DNA_polymerase
DNA_polymerase
Dna_polymerase
DNA_polymerases
DNA_polymerase_I
DNA_polymerase_III
DNA_polymerase_III_holoenzyme
DNA_primase
DNA_profiling
DNA_Repair
DNA_repair
DNA_repair
Dna_repair
DNA_repair.ogg
DNA_replication
DNA_replication
DNA_replication
Dna_replication
DNA_sequence
DNA_sequencer
DNA_sequences
DNA_sequencing
DNA_synthesis
DNA_test
DNA_testing
DNA_testing
Dna_testing
DNA_topology
DNA_transcription
DNA_transfer
DNA_Translation
DNA_transposable_element
DNA_vaccination
DNA_virus
DNA²
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