Question

In fruit flies, the allele for red eyes, R, is dominant. Which genotype represents a white-eyed male fruit fly?

A. XrXr
B. XrY
C. XRY
D. XRXr

Answer 1

the answer is B. XY is the male chromosome and the white allele ,r, is recessive

Answer 2

The correct answer would be B. XrY.

In fruit flies, XY codes for males and XX codes for females.

Gene encoding color of eyes is present in X chromosome only and carrier two alleles R and r.

In females, R is a dominant allele that codes for red eyes in homozygous as well as heterozygous condition whereas r is a recessive allele that codes for white eyes when present in homozygous condition only.

In males, only one X chromosome is present. So, if it carries R allele then the fruit fly would exhibit red eyes whereas if it carries r then the fruit fly would exhibit white eyes.

Only two out of four options are male fruit flies: XrY and XRY.

XrY would exhibit white eyes and XRY would exhibit red eyes.

Hence, we can conclude that XrY would be the white-eyed male fruit fly.