Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 2

Tracking a Series of Mutations. The following diagram shows the amino acids that result from mutations in the codon for a particular amino acid in a bacterial polypeptide:

Assume that each arrow denotes a single base-pair substitution in the bacterial DNA.
(a)Referring to the genetic code table in Figure 21-6, determine the most likely codons for each of the amino acids and the stop signal in the diagram.
(b)Starting with a population of mutant cells carrying the nonsense mutation, another mutant is isolated in which the premature stop signal is suppressed. Assuming wobble does not occur and assuming a single base change in the tRNA anticodon, what are all the possible amino acids that might be found in this mutant at the amino acid position in question