Assignment 4

The genetic phenomenon called epistasis occurs when the expression of one gene depends on or modifies the expression of another gene. In some cases of epistasis, one gene may completely mask or alter the expression of another gene. Perform the following crosses to study examples of epistasis in Drosophila.


1 .		Design and perform a cross between a female fly with vestigial wing size and a male fly with an incomplete wing vein mutation. Carefully study the phenotype of this male fly to be sure that you understand the effect of the incomplete allele. What did you observe in the F₁ generation? Was this what you expected? Why or why not? Once you have produced an F₁ generation, mate F₁ flies to generate an F₂ generation. Study the results of your F₂ generation, then answer the following questions.

2 .		Perform another experiment by mating a female fly with the apterous wing size mutation with a male fly with the radius incomplete vein structure mutation. Follow this cross to the F₂ generation. Which mutation is epistatic? Is the apterous wing mutation dominant or recessive?