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: $\begin{array} { | l | r | } \hline \text { wild-type } & 8 \\\hline \text { brown } & 241 \\\hline \text { bright-red } & 239 \\\hline \text { orange } & 12 \\\hline & 500 \\\hline\end{array}$
What is the genotype of the mother of these progeny?

Question

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}

What is the genotype of the mother of these progeny?

Quizplus · Accepted Answer

The mother must be heterozygous for both genes to produce the observed phenotypic ratios in the progeny. The presence of wild-type, brown, bright-red, and orange-eyed offspring suggests that the mother carries one wild-type allele for each gene and one mutant allele for each gene, allowing for all possible combinations when crossed with an orange-eyed male (who must be homozygous recessive for both traits). Option C correctly represents a heterozygous condition for both the pr and cn genes.

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