Question

Given below is the cross that Morgan performed on Drosophila, considering the gene for eye colour for his study. Study the results properly and suggest a possible cross to obtain a white eyed female.

• A. Cross between parental female and $F_1$ male
• B. Cross between parental male and $F_1$ female
• C. Cross between $F_1$ males and females
• D. No such cross is possible

Answer 1

The correct option is B Cross between parental male and $F_1$ female

The answer to this question is quite simple. We are asked to suggest a possible cross to obtain a white eyed female. Let’s start with the bottom. The genotype of the white eyed female would be $X^w{X}^w$, since white eye colour is recessive and will require 2 identical copies for its expression. Now let’s try to attempt each of the following crosses given in the options to find out the possibility of a white eyed female genotype.

So, we can see from the crosses, that in option b, the cross between parental male and $F_1$ female can give rise to a white eyed female. Hence option b is correct.