Essential Genetics 6th Edition by Daniel Hartl

Exercise 4

Gene conversion results from mismatch repair in a heteroduplex DNA molecule that gives rise to fungal asci with ratios of alleles such as 3 A : 1 a and 1 A : 3 a , instead of 2 A : 2 a.
(a) Why is a ratio of 2 A : 2 a expected?
(b) Why, among a large number of gametes chosen at random, is the Mendelian segregation ratio of 1 A : 1 a still observed in spite of gene conversion?