In codominant inheritance, which statement is true?

In codominant inheritance, which statement is true?

• A. A single allele masks the other
• B. Only the environment determines the phenotype
• C. Both alleles in a heterozygote are fully expressed in the phenotype
• D. The trait is only present in one sex

Answer: (C)

In codominance, both alleles are expressed in the phenotype of the heterozygote. This means neither allele masks the other, and you can see the effects of both alleles in the organism. A classic example is the ABO blood group system: individuals with one A allele and one B allele express both A and B antigens on their red blood cells, producing the AB phenotype. That simultaneous expression of both alleles is what codominance describes. The other statements don’t fit codominance: one allele masking the other describes complete dominance rather than codominance; phenotype determined solely by the environment isn’t about how alleles are expressed; and a trait limited to one sex points to sex-linked or sex-limited inheritance, not codominance.

In codominance, both alleles are expressed in the phenotype of the heterozygote. This means neither allele masks the other, and you can see the effects of both alleles in the organism. A classic example is the ABO blood group system: individuals with one A allele and one B allele express both A and B antigens on their red blood cells, producing the AB phenotype. That simultaneous expression of both alleles is what codominance describes.

The other statements don’t fit codominance: one allele masking the other describes complete dominance rather than codominance; phenotype determined solely by the environment isn’t about how alleles are expressed; and a trait limited to one sex points to sex-linked or sex-limited inheritance, not codominance.