Question

If a female fruit fly heterozygous for red eyes (X RX r) crossed with a white-eyed male (X rY), what percent of their offspring would have white eyes? (Draw a Punnett Square.)

Answer 1

6.25%

Step-by-step explanation:

Given that:

The trait of a female fruit fly that is heterozygous for red eyes = XRXr; &

The trait of a white-eyed male is XrY_ ;

since Y is dominant y; the male trait can either be XrYR or XrYr

So, let assume that it is XrYr

Then; if each trait self crossed; we have:

XRXr = XX Xr XR Rr

XrYr = XY Xr rY rr

Thus, the punnet Square can be computed as:

XX Xr XR Rr

XY XXXY XXYr XXYR XRYr

Xr XXXr XXrr XXRr XRrr

rY XrYX XxYr XrYR RrYr

rr XrXr Xrrr XrRr Rrrr

∴

the percentage of offspring that would have white eyes XrY_ is:

1/16 = 0.0625

= 6.25%