Question

In fruit flies, the gene for eye color is located on the X chromosome, and the red eye allele is dominant over the white eye allele A female fly with genotype XRXr is mated with a male fly with genotype XrY. Which statement below best describes the expected outcome of this cross?

Answer 1

b. The chance of an offspring having white eyes is 50%.

Step-by-step explanation:

a. The chance of an offspring having red eyes is 75%.

b. The chance of an offspring having white eyes is 50%.

c. The chance that a male offspring will have white eyes is 0%.

d. The chance that a female offspring will have red eyes is 100%.

Gene for eye color is X-linked.

Red allele R is dominant over white allele r.

`X^RX^r` female is crossed with
`X^rY` male:

`X^RX^r` x
`X^rY` =
`X^RX^r, X^RY, X^rX^r and X^rY`

50% of the offspring has red eye (
`X^RX^r and X^RY`) while the remaining 50% has white eye (
`X^rX^r and X^rY`).

Hence,

The chance of an offspring having white eye is 50%

The chance of an offspring having red eye is 50%

The chance of a male offspring having white eye is 50% and not 0%

The chance of a female offspring having red eye is 50% and not 100%

The correct option is b.