Arizona State University (ASU) BIO182 General Biology II Exam 2 Practice

Incomplete dominance is characterized by heterozygotes exhibiting an intermediate phenotype that is distinct from the phenotypes of both homozygotes. In this genetic scenario, when an individual inherits two different alleles for a trait, rather than one allele completely masking the other (which would be complete dominance), the resulting phenotype is a blend of the two. This blending can often be observed in examples such as flower color in snapdragons, where a red flower crossed with a white flower produces offspring with pink flowers, demonstrating that neither color is fully dominant over the other.

This concept differentiates incomplete dominance from complete dominance, where heterozygotes would display only the dominant trait. In cases of incomplete dominance, instead of having the same phenotype as one of the homozygous parents, the heterozygous offspring possess a unique phenotype that represents a mix of both parental traits. This intermediate expression is a key feature that illustrates the principle of incomplete dominance effectively.