Question

why are white - eyed female fruit flies so rare in nature?
white - eyed females are not rare,
the allele for white eyes was nearly removed from the gene pool,
females must inherit two copies of the recessive allele,

Explanation:

In fruit flies, eye - color is a sex - linked trait. The gene for eye - color is located on the X chromosome. Females have two X chromosomes (\(XX\)), and males have one X and one Y chromosome (\(XY\)). The allele for white eyes (\(w\)) is recessive. For a female to have white eyes (\(X^{w}X^{w}\)), she must inherit the recessive allele (\(X^{w}\)) from both her father (\(X^{w}Y\) - he can only pass on \(X^{w}\) to his daughters) and her mother (\(X^{w}X^{-}\) - the mother must have at least one \(X^{w}\) allele). In nature, it is less likely for a female to inherit two copies of the recessive allele compared to males (who only need to inherit one copy of the recessive allele on their single X chromosome, \(X^{w}Y\)) to show the white - eye phenotype.
The first option “White - eyed females are not rare” is incorrect as per the genetic mechanism described. The second option “The allele for white eyes was nearly removed from the gene pool” is not relevant to the rarity of white - eyed females.

Answer:

C. Females must inherit two copies of the recessive allele.