Dominant mutations curly (Cy) in the Cy^+ gene results in flies with curly wings

Question

Dominant mutations curly (Cy) in the Cy^+ gene results in flies with curly wings. A dominant mutation (Sco) in the Sco^+ gene results in flies with fewer bristles. Sco flies with normal wings were crossed to flies with curly wings and normal bristles. Both Cy^+ and Sco^+ loci are located on the second chromosome. Assuming not recombination, the expected progeny and their proportions are: (a) Cy: Sco mutant flies will appear in 1: 1 ratio b) flies with Sco (fewer) bristles only. (c) flies with curly wings only (d) neither Sco bristles, nor curly wings (wild type) (e) flies of all categories (Sco only, Cy only, wild type and double mutant) in a 1: 1: 1: 1 ratio.

Explanation / Answer

Answer: e). Flies of all categories (Sco only, Cy only, Wild type and Double mutants) in a 1:1:1:1

Explanation:

Sco flies with normal wings X Curly wings with normal bristles

Sco cy+/Sco+ cy+      X Sco+ cy+/Sco+ cy----Parents

Sco+ cy+

Sco+ cy

Sco cy+

Sco cy+/ Sco+ cy+ (Sco only, 25%)

Sco cy+ / Sco+ cy (Double mutants, 25%)

Sco+ cy+     

Sco+ cy+ / Sco+ cy+ (wild, 25%)

Sco+ cy+ / Sco+ cy (Cy only, 25%)

Sco only : Cy only : Wild type : Double mutants = 1:1:1:1

Sco+ cy+

Sco+ cy

Sco cy+

Sco cy+/ Sco+ cy+ (Sco only, 25%)

Sco cy+ / Sco+ cy (Double mutants, 25%)

Sco+ cy+     

Sco+ cy+ / Sco+ cy+ (wild, 25%)

Sco+ cy+ / Sco+ cy (Cy only, 25%)

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