Codominance occurs when both alleles of a gene are expressed in an individual (e.g., Black and White speckled). Which choice best describes codominance?

• A. Codominance
• B. Incomplete dominance
• C. Dominance
• D. Non-Mendelian inheritance

Answer: (A)

Codominance is the idea that in a heterozygous individual, both alleles are expressed in the phenotype. In a Black and White speckled trait, you see both colors present at the same time as distinct patches, not a blend like gray. This is different from incomplete dominance, where the heterozygote shows an intermediate phenotype (for example, pink from red and white). It’s also different from simple dominance, where one allele masks the other. Non-Mendelian inheritance is a broad term, but codominance specifically describes the situation where both alleles contribute visibly and equally to the phenotype.