Question

Miniature wings in Drosophila are due to an X-linked allele (Xm) that is recessive to the wild-type allele for normal long wings (X+). Brown eyes are produced by an autosomal allele (bw) which is recessive to the wild-type allele for red eyes (bw+). A female that is homozygous for normal wings and has brown eyes is crossed with a male that has miniature wings and is homozygous for red eyes. The F1 offspring are intercrossed to produce the F2 generation. What proportion of the F2 males are expected to have miniature wings and brown eyes?

Answer 1

In the F2 generation, 25% of the males are expected to have miniature wings and brown eyes.

Step-by-step explanation:

In Drosophila, miniature wings are due to an X-linked recessive allele (Xm) that is recessive to the wild-type allele for normal long wings (X+). Brown eyes are produced by an autosomal recessive allele (bw) that is recessive to the wild-type allele for red eyes (bw+). When a female that is homozygous for normal wings and has brown eyes is crossed with a male that has miniature wings and is homozygous for red eyes, in the F1 generation, all offspring will have normal wings and red eyes. When the F1 offspring are intercrossed to produce the F2 generation, the proportion of F2 males expected to have miniature wings and brown eyes would be 25%. This is because 1/4 of the F2 males will have the genotype XmYbw and would exhibit both the recessive traits.

Answer 2

1/16

Step-by-step explanation:

Given,

X+, Xm = X linked

bw+ , bw = autosomal

Female parent : X+X+bwbw ( normal wings and brown eyes )

Male parent : XmYbw+bw+ ( miniature wings and red eyes )

When X+X+bwbw X XmYbw+bw+ :

F1 females are X+Xmbw+bw ( normal wings, red eyes )

F1 males are X+Ybw+bw ( normal wings, red eyes )

When X+Xmbw+bw X X+Ybw+bw :

Out of the total progeny 1/2 will be males. Out of them 1/2 will have miniature wings. Out of them 1/4 will have brown eyes.

So, proportion of F2 males with miniature wings and brown eyes will be:

1/2 X 1/2 X 1/4 = 1/16