Question

A laboratory mouse homozygous for an RFLP marker is mated to a wild mouse that is heterozygous for that marker. One of the heterozygous individuals resulting from this cross is mated back to the wild parent. What proportion of the offspring will have the same RFLP pattern as the original laboratory mouse?

Answer 1

Answer:

1/4

Explanation:

Let the RFLP marker gene be represented by R.

Homozygous laboratory mouse will be RR

Heterozygous wild mouse will be Rr

A mating between homozygous and heterozgous individuals will be:

                         RR         x               Rr

F1 progenies will be: RR, Rr, RR, Rr which is equivalent to 2RR (homozygous) and 2Rr (heterozygous)

One of the F1 heterozygous (Rr) is now backcrossed with wild parent (Rr)

                          Rr            x              Rr

Resulting in: RR, 2Rr, rr

Hence, the proportion of the offspring that will have the same RFLP pattern as the original laboratory mouse (RR) will be 1 out of 4 or 1/4.

See the attached image for the punnet square analysis