Question

In fruit flies, the gene for red eyes (R) is dominant and the gene for sepia eyes (r) is recessive. If two red-eyed heterozygous flies (Rr) mate together, what are the possible genotypes of their offspring? (Hint: You many want to complete a Punnett square.)

RR and Rr

Rr only

RR and rr

RR, Rr, and rr

Answer 1

That is how you make a Punnett Square.

The problem asked us to cross two flies with the same genotype, together.

(R r) and (R r)

So you see on the top of the Punnett Square, we have one of the parents. (R r)

And on the left side of the Punnett Square, we have the other parent. (R r)

And when we cross them together, we get four squares, with one genotype in each square.

Those four squares represent the genotypes of the offspring.