Which pattern of inheritance involves expression of both alleles in the phenotype without blending or dominance?

Which pattern of inheritance involves expression of both alleles in the phenotype without blending or dominance?

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

Answer: (A)

Codominance is when both alleles are expressed in the phenotype of a heterozygote, and there’s no blending or dominance. The organism shows both traits distinctly rather than a mix. A classic example is blood type AB, where the A and B alleles each produce their own antigen, so individuals with IAIB have both A and B antigens on red blood cells. In incomplete dominance, you’d see a blended intermediate phenotype (like red plus white making pink). In complete dominance, one allele masks the other, so the dominant trait appears in the phenotype even though the other allele is present. Epistasis involves interactions between different genes, where one gene's product can mask or modify the effect of another gene. This description fits codominance.

Codominance is when both alleles are expressed in the phenotype of a heterozygote, and there’s no blending or dominance. The organism shows both traits distinctly rather than a mix. A classic example is blood type AB, where the A and B alleles each produce their own antigen, so individuals with IAIB have both A and B antigens on red blood cells. In incomplete dominance, you’d see a blended intermediate phenotype (like red plus white making pink). In complete dominance, one allele masks the other, so the dominant trait appears in the phenotype even though the other allele is present. Epistasis involves interactions between different genes, where one gene's product can mask or modify the effect of another gene. This description fits codominance.