Which inheritance pattern occurs when one allele is not completely dominant over another, resulting in an intermediate phenotype?

Which inheritance pattern occurs when one allele is not completely dominant over another, resulting in an intermediate phenotype?

• A. Incomplete dominance
• B. Codominance
• C. Complete dominance
• D. Epistasis

Answer: (A)

When one allele is not completely dominant over another, the heterozygote shows an intermediate phenotype rather than a trait that looks like either parent. This blending occurs because the products of both alleles contribute to the trait in roughly equal, but not fully dominant, amounts. A classic example is flower color: red crossed with white can produce pink flowers, illustrating the intermediate phenotype. This differs from codominance, where both traits are expressed together and distinctly (you can see both red and white areas at the same time). It also differs from complete dominance, where the dominant allele completely masks the other in the phenotype, and from epistasis, where one gene at a different locus affecting the expression of another gene changes the outcome.

When one allele is not completely dominant over another, the heterozygote shows an intermediate phenotype rather than a trait that looks like either parent. This blending occurs because the products of both alleles contribute to the trait in roughly equal, but not fully dominant, amounts. A classic example is flower color: red crossed with white can produce pink flowers, illustrating the intermediate phenotype.

This differs from codominance, where both traits are expressed together and distinctly (you can see both red and white areas at the same time). It also differs from complete dominance, where the dominant allele completely masks the other in the phenotype, and from epistasis, where one gene at a different locus affecting the expression of another gene changes the outcome.