What fraction of the offspring from a SsYy x SsYy cross are predicted to be heterozygous for both characteristics?

To determine the fraction of offspring from a cross between two individuals, each with the genotype SsYy, that are heterozygous for both characteristics, we can approach this with a Punnett square analysis.

In this cross, SsYy indicates that each parent carries one allele for each gene: S (dominant), s (recessive) for the first trait, and Y (dominant), y (recessive) for the second trait. The possible gametes produced by each parent can be listed as SY, Sy, sY, and sy.

When we create a Punnett square combining these gametes, we will have the following combinations of genotypes for the offspring:

• SSYY

• SSYy

• SsYY

• SsYy

• SsYy

• sSYy

• ssYY

• ssYy

• ssYy

• syy

From the completed Punnett square, we can count how many offspring are heterozygous for both traits. The heterozygous combinations are SsYy (which appears twice), meaning there are 3 occurrences out of a total of 16 possible combinations.

Consequently, the fraction of the offspring that are