question_answer

In fruitflies, a sex-linked gene controls the development of eye colour. The eyes are either red or white. The male is the heterogametic sex. What will be the expected percentage of eye colours in the progeny when a heterozygous red-eyed female is crossed with a white-eyed male?

A)

Red eyes		White eyes
Male	Female	Male	Female
25.0	25.0	25.0	25.0

B)

Red eyes		White eyes
Male	Female	Male	Female
37.5	37.5	12.5	12.5

C)

Red eyes		White eyes
Male	Female	Male	Female
12.5	12.5	37.5	37.5

D)

Red eyes		White eyes
Male	Female	Male	Female
0	50.0	50.	0

Correct Answer: B

Solution :

\[{{F}_{1}}\,genotypes\,:{{X}^{R}}{{X}^{r}}{{X}^{r}}{{X}^{r}}\,\,\,{{X}^{R}}Y\,\,\,\,{{X}^{r}}Y\] \[{{F}_{1}}\]phenotype:  red F, white F, red M. white M