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Revision as of 23:27, 12 April 2005

PLEASE, PLEASE try to refrain from transforming this section into another highly-accurate-but-impossible-to-read one! It has been assumed from the beginning that this is not necessarily a very accurate description, and that it's only meant as a generic overview.

Misplaced Pages needs to be accurate, but it can be simple and accurate. Dumbing down something too much (which I'm not saying is happening here) is also to be avoided. --Lexor|Talk

This is what most people need, and that's why it has been inserted at the top of the article. If you find that curious, or even absurd, think how you would feel if some article which pertains to scientific dissection in a field you don't master only contained scientific data -- that would be frustrating, wouldn't it?

Thank you for understanding!

--Gutza 11:47, 5 Oct 2004 (UTC)

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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 regulate genes, and areas that either have no function, or a function we do not (yet) 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 (adenine, thymine, cytosine, and guanine, respectively); 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 sequence itself is the description for genes;
• 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 scientists 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 tandom repeats and minisatellites are compared. DNA profiling was developed in 1984 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.