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1. Two red-eyed Drosophila are mated, and their progeny show a 3:1 ratio of red to...

1. Two red-eyed Drosophila are mated, and their progeny show a 3:1 ratio of red to white, but the whites are all males. Letting "A" be red and "a" white, the parents can best be represented as:

A. A/a female x A/a male

B. A/a female x a/a male

C. A/a x a/Y

D. A/a x A/Y

E A/A x a/Y

2. We have dealt mainly with only two genes, but the same principles hold for more than two genes. Consider the following cross: A/a ; B/b ; C/c ; D/d ; E/e X a/a ; B/b ; c/c ; D/d ; e/e. Assuming independent assortment, what proportion of progeny will phenotyically resemble wild type?

A. Pr = 9/218

B. Pr = 55/128

C. Pr = 9/64

D. Pr = 55/64

E. Pr = 119/128

F. Pr = 1/32

G. Pr = 1/64

H. Pr = 1/128

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Answer #1

Ans. As it follows a 3:1 progeny ratio of red to white. Hence there would be three dominant traits and one recessive trait. As per the punnette square the alleles would be represented as AA, Aa, Aa and aa. Hence the most appropraite option would be option A A/a female x A/a male.

Ans. The correct option is option C Pr = 119/128

A/a x a/a = 1/2

B/b x B/b = 3/4

C/c x c/c = 1/2

D/d x D/d = 3/4

E/e x e/e = 1/2

Multiplying these probability we will get as normal progeny = 9/128.

Hence the wild type progeny would be 128-9 = 119

Therefore Pr = 119/128.   

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