Chapter 5, Problem 39P

A cross was performed between one haploid strain of yeast with the genotype a f g and another haploid strain with the genotype α f⁺ g⁺ (a and α are mating types). The resulting diploid was sporulated, and a random sample of 101 of the resulting haploid spores was analyzed. The following genotypic frequencies were seen:

α f+ g+	31
a f g	29
a f+ g+	14
α f g	13
a f+ g	6
α f g+	6
a f+ g+	1
α f g	1

a.	Map the loci involved in the cross.
b.	Assuming all three genes are on the same chromosome arm, is it possible that a particular ascus could contain an α f g spore but not an a f g spore? If so, draw a meiosis that could generate such an ascus.