Indicate the percentage of tetrads that would have 0, 1, 2, 3, or 4 viable spores after Saccharomyces cerevisiae a / α diploids of the following genotypes are sporulated: a. A true-breeding wild-type strain (with no mutations in any gene essential for viability).

b. A strain heterozygous for a null (completely inactivating) mutation in a single essential gene.

For the remaining parts of this problem, consider crosses between yeast strains of the form a × b, where a and b are both temperature-sensitive mutations in different essential genes. The cross is conducted under permissive (low-temperature) conditions. Indicate the percentage of tetrads that would have 0, 1, 2, 3, or 4 viable spores subsequently measured under restrictive (high-temperature) conditions.

c. a and b are unlinked, and both are 0 m. u. from their respective centromeres.

d. a and b are unlinked; a is 0 m. u. from its centromere, while b is 10 m. u. from its centromere.

e. a and b are 0 m. u. apart.

f. a and b are 10 m. u. apart. Assume all crossovers between a and b are SCOs (single crossovers).

g. In part (f), if a four-strand DCO (double crossover) occurred between a and b, how many of the spores in the resulting tetrad would be viable at high temperature?