Question

If a homozygous individual expressing the dd genotype for a trait is crossed with a heterozygous dd individual, what percentage of the resulting offspring, on average, would be expected to exhibit the recessive phenotype?

Answer 1

I think you meant the heterozygous individual had the alleles of Dd, not dd, because that would not be heterozygous.

Using the homozygous alleles (dd) and heterozygous alleles (Dd) we can input these into a punnett square.

See punnett square attached. As you can see, when crossing a heterozygous (Dd) parent and homozygous (dd) parent, the offspring have a 100% of exhibiting the recessive phenotype.

All of the offspring have a lowercase d in their alleles, which indicates the recessive phenotype.

Your answer is 100%.