What term describes a trait that is intermediate between the phenotype of the two parents because the dominant allele is unable to express itself fully?

• A. Co dominance
• B. Incomplete dominance
• C. Polygenic trait
• D. Sex determined

Answer: (B)

Incomplete dominance describes a situation where neither allele is fully dominant, so the offspring’s phenotype in the heterozygous state is a blend between the two parental phenotypes. The dominant allele doesn’t completely mask the other allele, leading to an intermediate trait rather than one phenotype fully prevailing. A classic example is red x white flowers producing pink offspring in snapdragons. This differs from co-dominance, where both alleles are expressed simultaneously and distinctly (like AB blood types), and from polygenic traits, where many genes influence a trait, or from sex-determined traits tied to sex chromosomes.