Problems from textbook

13.18

The streptomycin sensitive strain should be exposed to a mutagen (such as UV light or radiation) to create mutants that may be resistant to streptomycin. Next, prepare a plate that has streptomycin. The bacterial colonies that grow on this plate will all be resistant to streptomycin. Now, make a copy of these colonies using replica plating. Transfer the colonies to a plate that does not contain streptomycin. The colonies that grow on the plate without streptomycin are the strain that can live with or without streptomycin. The colonies that do not grow on the plate without streptomycin cannot live without streptomycin.

13.40

The original polypeptide strain and the double mutant differ in two amino acids. The Lys-Gly amino acids in the original polypeptide become Glu-Arg in the double mutant. The Lys-Gly amino acid sequence is:

AAA-GGG

By adding a G before the first A in the initial AAA sequence, and by deleting the final G, we get:

GAA-AGG

The resulting sequence codes for Lys-Arg.

The entire nucleotide sequence in the double mutant is:

5’ – AUG CCC UUU GGG GAA AGG UUU CCC UAA—3’

14.8

There are two genes.

Gene 1: mutants 1,2,3,4,5,6,8
Gene 2: mutants 7

14.14

A cis-trans test can be performed to determine whether the two varieties are the results of mutations on the same gene, or on different genes. First, it is necessary to ensure that each white variety is true-breeding. Next, we need to perform a cis test on each white variety by crossing individuals from each white strain with individuals from the wild-type strain. The progeny should be wild-type. Wild-type progeny indicate that the mutations that cause the white varieties are recessive. If the cis test produces wild-type offspring, we can proceed to the trans test. In the trans test, we cross true-breeding individuals