In Fruit Flies,the Recessive Pr and Cn Mutations Cause Brown

question 66

Multiple Choice

In fruit flies,the recessive pr and cn mutations cause brown and bright-red eyes,respectively (wild-type flies have brick-red eyes) .The double mutant pr cn combination has orange eyes.A female who has wild-type eyes is crossed to an orange-eyed male.Their progeny have the following distribution of eye colours: $$\begin{array} { | l | r | } \hline \text { wild-type } & 8 \\\hline \text { brown } & 241 \\\hline \text { bright-red } & 239 \\\hline \text { orange } & 12 \\\hline & 500 \\\hline\end{array}$$
The mother of these progeny resulted from a cross between two flies from true breeding lines.What are the genotypes of these two lines?

• A) pr pr cn⁺ cn⁺ and pr⁺ pr⁺ cn cn
• B) pr⁺ pr⁺ cn⁺ cn⁺ and pr pr cn cn
• C) pr⁺ pr cn⁺ cn and pr pr cn cn
• D) pr⁺ pr cn cn and pr pr cn⁺ cn
• E) Either pr pr cn⁺ cn⁺ and pr⁺ pr⁺ cn cn or pr⁺ pr⁺ cn⁺ cn⁺ and pr pr cn cn could be true.

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