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Beginning Perl for Bioinformatics by James Tisdall

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The Genetic Code

The describes how the information in the coding regions of DNA is translated into the correct amino acids for the assembly of the cell's proteins.

Background

Here is a short introduction for the nonbiologists.

As stated earlier, DNA encodes the primary structure (i.e., the amino acid sequence) of proteins. DNA has four nucleotides, and proteins have 20 amino acids. The encoding works by taking each group of three nucleotides from the DNA and "translating" them to an amino acid or a stop signal. Each group of three nucleotides is called a codon. We'll see in detail how this coding and translation works.

Actually, transcription first uses DNA to make RNA, and then translation uses RNA to make proteins. This is called the central dogma of molecular biology. But in this course, I'll abbreviate the process and somewhat inaccurately call the entire process from DNA to protein "translation."

The reason for this cavalier distinction is that the whole business is much easier to simulate on computer using strings to represent the DNA, RNA, and proteins. In fact, as shown in Chapter 4, transcribing DNA to RNA is very easy indeed. In your computer simulations, you can simply skip that step, since it's just a matter of changing one letter to another. (The actual process in the cell, of course, is much more complex.)

Note that with four kinds of bases, each group of three bases of DNA can represent as many as 4 x 4 x 4 = 64 possible amino acids. Since there are only 20 amino ...

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