What term describes when both alleles for a gene are fully expressed?

What term describes when both alleles for a gene are fully expressed?

• A. Co dominance
• B. Incomplete dominance
• C. Dominant trait
• D. True breeding

Answer: (A)

Codominance describes a situation where both alleles for a gene are fully expressed in the phenotype. In a heterozygous individual, you see both traits rather than a blended result or one trait masking the other. A classic example is the AB blood type, where both A and B antigens are present on red blood cells. This differs from incomplete dominance, which would produce an intermediate phenotype (like pink from red and white). It also differs from a dominant trait, where one allele masks the other, and from true breeding, which refers to organisms that are homozygous and produce uniform offspring.

Codominance describes a situation where both alleles for a gene are fully expressed in the phenotype. In a heterozygous individual, you see both traits rather than a blended result or one trait masking the other. A classic example is the AB blood type, where both A and B antigens are present on red blood cells. This differs from incomplete dominance, which would produce an intermediate phenotype (like pink from red and white). It also differs from a dominant trait, where one allele masks the other, and from true breeding, which refers to organisms that are homozygous and produce uniform offspring.