Question

Punnett squares are used to show possible combinations of alleles or to predict the probability of a trait occurring in offspring. An incomplete dominance cross is performed between a bird that is homozygous for red feathers and a bird that is homozygous for blue feathers. Purple offspring result. Then, two of the purple offspring are crossed. According to the Punnett square for this cross, how many of the offspring from the second cross will have a feather color that results from incomplete dominance?

Answer 1

The answer is two. In incomplete dominance, heterozygotes have a trait that is intermediary between dominant and recessive homozygote. Let allele A be dominant and allele a recessive allele. The genotypes and phenotypes are as following: genotype: AA - phenotype: dominant homozygote with red feathers, genotype: Aa - heterozygote with purple feathers, and genotype: aa - recessive homozygote with blue feathers. In the cross of two purple birds (Aa x Aa), we have 1 bird with genotype AA and red feathers, 2 birds with genotype Aa and purple feathers, and 1 bird with genotype aa with blue feathers.