In Drosophila, a cross was made between a yellow - bodied male with vestigial (not fully developed) wings and a wild-type female (brown body). The F1 generation consisted of wild-type males and wild-type females. F1 males and females were crossed, and the F2 progeny consisted of 16 yellow-bodied males with vestigial wings, 48 yellow-bodied males with normal wings, 15 males with brown bodies and vestigial wings, 49 wild-type males, 31 brown-bodied females with vestigial wings, and 97 wild-type females. Explain the inheritance of the two genes in question based on these results.

Question

Bernice

Biology

18 March, 17:33

In Drosophila, a cross was made between a yellow - bodied male with vestigial (not fully developed) wings and a wild-type female (brown body). The F1 generation consisted of wild-type males and wild-type females. F1 males and females were crossed, and the F2 progeny consisted of 16 yellow-bodied males with vestigial wings, 48 yellow-bodied males with normal wings, 15 males with brown bodies and vestigial wings, 49 wild-type males, 31 brown-bodied females with vestigial wings, and 97 wild-type females. Explain the inheritance of the two genes in question based on these results.

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Nellie · Answer 1

The body color gene is sex-linked and the vestigial gene is autosomal.

Explanation:

1st cross) yellow-bodied male with vestigial wings X wild-type female (brown body)

F1: wild-type males and females

2nd cross) F1 x F1

F2:

16 yellow-bodied males with vestigial wings

48 yellow-bodied males with normal wings

15 males with brown bodies and vestigial wings

49 wild-type males

31 brown-bodied females with vestigial wings

97 wild-type females

Total: 256

Let's analyze the traits (body color and wings) one at a time:

Wing shape

31 males and 31 females have vestigial wings 16 + 15 + 31 = 62 individuals with vestigial wings 97 + 49 + 48 = 194 individuals with normal wings

These proportions are similar to 1/4 vestigial, 3/4 normal wings. In addition, males and females have the same amount of individuals with vestigial wings. This suggests that the wing shape gene is autosomal, with the allele vg + being wild-type and dominant over the vestigial vg allele ...

Body color

64 yellow-bodied males, 0 yellow-bodied females 16 + 48 = 64 individuals have yellow bodies 15 + 49 + 31 + 97 = 192 individuals have brown (WT) bodies.

The ratios are also 1 yellow : 3 brown, but there's a difference between males and females. This suggests that the gene that determines body color is sex-linked.

With this hypothesis, let's do the crosses considering the genotypes:

1) Parents: XʸY vg vg X Xʸ⁺Xʸ⁺ vg + vg+

F1: Xʸ⁺Y vg vg + and Xʸ⁺Xʸ vg vg + (all wild-type)

2) F1xF1 gives us the offspring predicted in the Punnett Square, which matches the proportions observed in the F2.