Ascospores from a cross leu-2 * ad-7 met-3 (all auxotrophic markers)are plated on minimal medium (no adenine,leucine,or methionine).If the three genes are unlinked,what proportion of ascospores is expected to grow into a colony on this medium?
A)0.005
B)0.045
C)0.125
D)0.250
E)0.500

Question

Quizplus · Accepted Answer

If the genes are unlinked, each gene will independently assort. The probability of an ascospore being prototrophic for each gene is 1/4 (since each gene has a 1/2 chance of being wild type from each parent). Therefore, the probability of being prototrophic for all three genes is (1/4) * (1/4) * (1/4) = 1/64 = 0.015625, which is closest to 0.125.

Ascospores from a Cross Leu-2 * Ad-7 Met-3 (All Auxotrophic