Which term is used to describe the effect where neither allele masks the other, resulting in an intermediate phenotype?

• A. Polygenic inheritance
• B. Incompletely dominance
• C. Codominance
• D. Incomplete dominance

Answer: (D)

The phenomenon tested is when neither allele fully dominates in a heterozygote, producing an intermediate phenotype. This is incomplete dominance, where the offspring’s trait sits between the two parental traits because neither allele masks the other. A classic example is a cross between red- and white-flowered plants yielding pink flowers in the offspring.

This differs from codominance, where both alleles are expressed fully and separately in the phenotype (like AB blood type, where both A and B antigens are present). It also isn’t polygenic inheritance, which involves many genes contributing to a trait and typically results in a continuous range of phenotypes rather than a simple blend from two alleles.