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

Answer:

6.25%

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%