Question

Eyeless is a recessive gene on chromosome 4 of Drosophila melanogaster. Flies homozygous for ey have tiny eyes or no eyes at all. A male fly trisomic for chromosome 4 with genotype +/+/ey is crossed with a normal, diploid eyeless female.

What proportion of their progeny will be eyeless?

A. 1/6

B. 1/3

C. 1/2

D. 2/3

E. 1/8

F. 1/4

G. 3/8

H. 5/8

I. 3/4

Answer 1

A. 1/6

Step-by-step explanation:

A male fly trisomic for chromosome 4 with genotype +/+/ey is crossed with a normal, diploid eyeless female. i.e

δ +/+/ey ey/ey ⊕

+, +, +/+, ey, +/ey, +/ey × ey/ey

ey/+, +/ey, +/+/ey, ey/ey, +/ey/ey, +/ey/ey

ey/+, +/ey, +/+/ey, ey/ey, +/ey/ey, +/ey/ey

=2/12

=1/6