posted by stew .
need help with these genetics problems. please help with what you can. thanks:
Given that loci A and B in Drosophila are sex-linked and 20 map units apart, what phenotypic frequencies would you expect in male and female offspring resulting from the following crosses? (Assume A and B are dominant to a and b, respectively).
A) AaBb (cis) female X ab/Y male
B) AaBb (trans) X ab/Y male
C) aabb female X AB/Y male
Assume that a cross is made beyween AaBb and aabb plants, and the offspring occur in the following numbers: 106 AaBb, 48 Aabb, 52 aaBb, 94 aabb. These results are consistent with which arrangement of genes?
for 2a - cis means the AB is paired on the same chromosome and the ab is on the other. you would expect 80% females AB/ab and 20% females ab/ab. For males, 80% AB/Y and 20% ab/Y.
2b use the same logic as 2a, expect now the chromosomes are Ab and aB to start.
for 2c - it is all AB/ab females and all ab/Y males.