Question

how do i create a dihybrid cross for the genotypes YySs and yyss?

Answer 1

To start, come up with the possible combinations of alleles for each parent. For example, the YySs parent has two chromosomes with the first gene (Y) on it. One of these two chromosomes has Y and the other has y. It has two more chromosomes with the second gene (S) on it. One of these two chromosomes has S and the other has s.

Each gamete this parent makes needs one of each kind of chromosome. It needs one with a Y or y, and one with an S or s.

So the possible combinations are YS, Ys, yS or ys.

The combinations for the other parent (yyss) are easy. It has two chromosomes with recessive y alleles and two with recessive s alleles. So the possible combinations are ys, ys, ys, ys - all the same.

Answer 2

In addition to @blues point, you can do a Punett squeare like this

I hope this helps you to do the cross