Chapter 12, Problem 25PDQ

The genetic code is degenerate. Amino acids are encoded by either 1, 2, 3, 4, or 6 triplet codons. (See Figure 12–7.) An interesting question is whether the number of triplet codes for a given amino acid is in any way correlated with the frequency with which that amino acid appears in proteins. That is, is the genetic code optimized for its intended use? Some approximations of the frequency of appearance of nine amino acids in proteins in E. coli are

Amino Acid	Percentage
Met	2
Cys	2
Gln	5
Pro	5
Arg	5
lle	6
Glu	7
Ala	8
Leu	10

(a) Determine how many triplets encode each amino acid.

(b) Devise a way to graphically compare the two sets of information (data).

(c) Analyze your data to determine what, if any, correlations can be drawn between the relative frequency of amino acids making up proteins and the number of codons for each. Write a paragraph that states your specific and general conclusions.

(d) How would you proceed with your analysis if you wanted to pursue this problem further?