Draw the general structure of an amino acid.

The genetic code is described as degenerate.

What is meant by this? Use an example from Table 1 to illustrate your answer.

A scientist investigated changes in the amino acid sequence of a human enzyme resulting from mutations. All these amino acid changes result from single base substitution mutations. This enzyme is a polypeptide 465 amino acids long.

Table 2 shows the result of three of the base substitutions.

What is the minimum number of bases in the gene coding for this polypeptide?

Answer =

Use information from Table 1 to tick (✓) one box that shows a single base substitution mutation in DNA that would result in a change from Val to Ala at amino acid number 203

☐ CAA → CGA

☐ GUU → GCA

☐ GUU → GUC

☐ CAC → CGG

A change from Glu to Lys at amino acid 300 had no effect on the rate of reaction catalysed by the enzyme. The same change at amino acid 279 significantly reduced the rate of reaction catalysed by the enzyme.

Use all the information and your knowledge of protein structure to suggest reasons for the differences between the effects of these two changes.