192k views
3 votes
Which cross would result in a female white-eyed fruit fly? (The gene for white eyes is represented as "w".)

a. XXw * XY
b. XwXw * XY
c. XX * XwY
d. XXw * XwY
e. XXw * XYw

User BingeBoy
by
8.4k points

1 Answer

6 votes

Final answer:

The correct cross to produce a female fruit fly with white eyes is option b. XwXw * XY, where a homozygous white-eyed female mates with a male with either red or white eyes. The correct option is b.

Step-by-step explanation:

In Biology, specifically Mendelian genetics and the study of Drosophila melanogaster, or fruit flies, eye color is a classic example of an X-linked trait. The white-eye allele (w) is recessive to the red-eye allele.

As females have two X chromosomes (XX) and males have one X and one Y chromosome (XY), the manifestation of white eyes in females requires two copies of the white-eye allele, making them homozygous recessive (XwXw).

Therefore, when considering which cross would result in a female fruit fly with white eyes, we need to find a pairing that could produce an XwXw offspring.

The correct cross to produce a female white-eyed fruit fly is option b. XwXw * XY, where a homozygous white-eyed female (XwXw) mates with a male with either red (XWY) or white eyes (XwY).

The outcome of such a cross would give us a result where all female offspring would have white eyes, as they would inherit one white-eye allele from their mother and potentially another white-eye allele or red-eye allele from their father.

The white-eye allele from their mother guarantees that any X chromosome they inherit from their father that carries the white-eye allele will result in white-eyed female offspring.

User Mateen Kiani
by
8.2k points