Question

Mr. Joseph crosses a heterozygous red eyed female Drosophila with a white eyed male. What will be the characters of males and females after $F_1$ generation respectively?

• A. red eyed females and white eyed males
• B. 50% red and 50% white eyed female as well as males
• C. white eyed females and red eyed males
• D. 50% red and 50% white eyed females and 100% white eyed males

Answer 1

The correct option is B 50% red and 50% white eyed female as well as males

X chromosome in Drosophila contains the allele for eye color, a red eyed heterozygous female ($X^R{X}^r$) will have $X^R$ and $X^r$ gametes; while the white eyed male ($X^{r}Y$) will produce two types of gametes i.e $X^r$and Y. “R” (Red color) allele is dominant over “r” (white color). Following will be the possibility of combination on crossing these two:

Gametes	$X^R$	$X^r$
$X^r$	$X^R{X}^r$ Red eye female	$X^r{X}^r$ white eye female
Y	$X^{R}Y$ Red eye male	$X^{r}Y$ white eye male

Thus, 50% of male and female offspring are red and white eyed.