Two normal looking fruit flies were crossed and in the proge

Two normal looking fruit flies were crossed and in the progeny there were 202 females and 98 males. Provide a genetic explanation for this result including genotypes for the parents

Solution

Answer:

The expected sex ratio is 1:1, yet in this case seems to be 2:1. The female parent was heterozygous for an X-linked recessive lethal allele. This would result in 50 percent fewer males than females. Half of the female progeny should be heterozygous for the lethal allele and half should be homozygous for the nonlethal allele. Individually mate the F1 females and determine the sex ratio of their progeny. Of these F1 females, mated by normal males, half should produce normal male:female ratios (1:1), while the other half should produce a ratio of 2:1.

X^NXⁿ= Normal female

XⁿY=normal male