tetrads

Attached here is the set of questions that i found online. I can solve the questions except for the lastpart of question 3.

My answers for the 1st part of question one is 37 of the tetrads show parental ditype, 9 of them show tetratype while the rest (4） show non-parental ditype. From here, it is possible that drk1 and drk2 works in parallel to give the white colour phenotype. If either one of them is mutated, an intermediate phenotype ( light tan) could be observed. And from the information given on question c, we know that drk1 and drk2 mutations are on different gene.

However, when it comes to question d, I am confused about the two tetratype that occurs at the same frequency. It states that leu1 gene is closely linked to drk1, so, how can we get two different phenotypes that occurs at the same frequency when the two genes are closely linked? Is it ue to another gene locus or I was wrong from the 1st part of question?

Thanks for Helping.
Huan