Question

Cross Category 2: P1 - virgin white-eyed females x P2 - sepia-eyed males

A) Are the genes for white eyes and sepia eyes dominant or recessive?

B) Give the genotypes of P1 white-eyed females and P2 sepia-eyed males. Note: remember that two different genes are responsible for the white and sepia phenotypes.

C)Based on your answer to the previous question, please provide the expected phenotype and genotype of the F1 flies. Show your work. 16

D)What are the expected F2 phenotypic and genotypic ratio expected by crossing the F1 males and females? Show your work.

Answer 1

A) The genes for white eyes and sepia eyes are recessive.

B)

P1 white eyed females : X^wX^w

P2 sepia eyed males:X^sY

C) male

female	Xs	Y
Xw	XsXw wild type eyed female	XwY white eyed male
Xw	XsXw  wild type eyed female	XwY white eyed male

F1 genotype : X^sX^w : X^wY = 2:2 =1:1

F1 phenotype = wild type eyed female: white eyed male = 2:2=1:1

D)

F2: male

female	Xw	Y
Xs	XsXw wild type eyed female	XsY sepia eyed male
Xw	XsXw wild type eyed female	XwY white eyed male

Genotype ratio = X^sY : X^sX^w: :X^wY = 1:2:1

Phenotype ratio=sepia eyed male: wild type eyed female:white eyed male = 1:2:1