Molecular Evolution and Information

The Genetic Code

The coin code in table 3.1 applies to the four sided coin. The genetic code works in the same way, except instead of words the code specifies amino acids. The coin code groups the results of the coin tosses into groups of three. The genetic code does the same, except the letters are now chemicals. A group of three bases is called a codon. Each codon specifies an amino acid. For example, with the coin code:

TAC-CCA-TAA-AGA-ATC should be translated as follows: The dog is lazy.

but with the genetic code ( see table 3.2)

TAC-CCA-TAA-AGA-ATC should be translated as follows: methionine-glycine- isoleucine-serine.
   
    So the coin code specified words, and the genetic code specifies amino acids. Table 3.2 lists the genetic code, and figure 3.7 shows the process of transcription in which DNA is use to create RNA. Notice that in figure 3.7 the coding DNA strand creates a complementary RNA strand (G is replaced with C, C is replaced with G, T is replaced with A, and A is replaced with a new chemical unique to RNA - uracil or U for short).

Table 3.2: The Genetic Code

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