Homework Help: Bio

Posted by Amber on Wednesday, February 13, 2013 at 1:13pm.

In Drosophila, sepia colored eyes are due to a recessive allele s and wild type (red eye color) to its dominant allele s+. Sepia-eyed females are crossed to pure wild type males. What phenotypic and genotypic ratios are expected if the F1 males are then backcrossed to sepia-eyed parental females?

Bio - Devron, Wednesday, February 13, 2013 at 5:22pm
I'm assuming that eye color is sex-linked.

X^s+= dominant
X^s= recessive

The P1 generation:
Male: X^s+, Y
Female: X^s, X^s

P1 generation cross: [X^s, X^s] x [X^s+, Y]

F1 generation
1/2-X^s, X^s+
1/2-X^s+, Y

Cross of F1 males with P1 females:[X^s, X^s] x [X^s, Y]

F-2 generation:
1/2-X^s, X^s
1/2-X^s, Y

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