Chapter 4, Problem 28P

Yeast are single-celled eukaryotic organisms that grow in culture as either haploids or diploids. Diploid yeast are generated when two haploid strains fuse together. Seven haploid strains of yeast exhibit similar growth habit: At $\text{25°C,}$ each strain grows normally, but at $\text{37°C}$, they show different growth capabilities. The table below displays the growth pattern.

Describe the nature of the mutation affecting each of these mutant yeast strains. Explain why strains B and G display different growth habit at $\text{37°C}$ than the other strains. b. Each of the mutant pairs of haploid yeast is fused, and the resulting diploids are tested for their ability to grow at $\text{37°C}$. The results of the growth experiment are shown below.

How many different genes are mutated among these seven yeast strains? Identify the strains that represent each gene mutation.