Chapter 5, Problem 42P

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 $a\times b$, 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 the centromere.
d.	a and b are unlinked; a is 0 m.u. from the centromere, while b is 10 m.u. from the 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?