In a heterozygous individual, the allele that masks the expression of the other allele is called the

• A. Recessive
• B. Dominant
• C. Codominant
• D. Incomplete dominance

Answer: (B)

Dominance in genetics: when two different alleles are present, one can mask the expression of the other in the organism’s phenotype. The allele that does the masking is the dominant allele, and it determines the trait you observe in a heterozygous individual. For example, if the tall trait is governed by a dominant allele and the short trait by a recessive allele, a plant with a tall phenotype can have the genotype for tall even if it carries the recessive short allele as well (heterozygous). The other allele is the recessive one, which only shows up when two recessive copies are present.

Codominance and incomplete dominance describe different relationships between alleles, where both alleles influence the trait in distinct ways or form an intermediate phenotype, rather than one masking the other. Recessive refers to the allele that is masked in a heterozygote, not the one doing the masking.