When an allele is dominant, what phenotype is expected in a heterozygous individual?

• A. The dominant phenotype appears.
• B. The recessive phenotype appears.
• C. An intermediate phenotype appears.
• D. The phenotype cannot be predicted.

Answer: (B)

In a heterozygous individual, the dominant allele masks the expression of the recessive allele, so the phenotype shown is the one associated with the dominant trait. If the genotype is Aa, the dominant allele A determines the phenotype, such as tall height in a plant if tall is the dominant form. The recessive phenotype only appears when both copies are recessive (aa). An intermediate phenotype appears only in cases of incomplete dominance, which isn’t the default for simple dominance. So, the expected phenotype in a heterozygous individual is the dominant trait expressed.