Chapter 6, Problem 22P

An attribute of growth behavior of eight bacteriophage mutants ( $\text{1 to 8}$) is investigated in experiments that establish coinfection by pairs of mutants. The experiments determine whether the mutants complement one another (+) or fail to complement (−). These eight mutants are known to result from point mutation. The results of the complementation tests are shown below.

a. How many genes are represented by these mutations?

b. Identify the mutants of each gene.

c. In each coinfection above that is identified as a failure to complement (−), researchers see evidence of recombination producing wild-type growth. How do the researchers distinguish between wild-type growth resulting from complementation and wild-type growth that is due to recombination?

d. A new mutation, designated $\text{9}$, fails to complement mutants $\text{1, 3, 5, 7,}$ and $\text{8}$. Wild-type recombinants form between mutant $\text{9}$ and mutations $\text{3, 5,}$ and $\text{8}$; however, no wild-type recombinants form between mutant $\text{9}$ and mutations $\text{1 and 7}$. What kind of mutation is mutant $\text{9}$? Explain your reasoning.

e. New mutation $\text{10}$ fails to complement mutants $\text{1, 4, 5, 6, 8,}$ and $\text{9}$. Mutant $\text{10}$ forms wild-type recombinants with mutants 1, 5, and 6, but not with mutants $\text{4 and 8}$. Mutant $\text{9}$ and mutant $\text{10}$ form wild-type recombinants. What kind of mutation is mutant $\text{10}$? Explain your reasoning.

f. Gene mapping information identifies mutations $\text{2 and 3}$ as the flanking markers in this group of genes. Assuming these mutations are on opposite ends of the gene map, determine the order of mutations in the region of the chromosome.