A genetic trait is considered dominant if expressed when only one copy of the gene is present.

• A. Codominant Trait
• B. Dominant Trait
• C. Polygenic Trait
• D. Recessive Trait

Answer: (B)

Dominance describes how an allele influences phenotype when there are two copies of the gene. If a single copy is enough to express the trait, that allele is dominant over the alternate allele. The described statement matches this pattern: a trait appears even when only one copy of the allele is present, which is the hallmark of a dominant trait. In a heterozygous individual (one dominant and one recessive allele), the dominant allele masks the recessive one, so the dominant phenotype is shown. By contrast, a codominant trait would express both alleles’ effects in the heterozygote, a polygenic trait involves many genes contributing to variation, and a recessive trait expresses only when two copies of the recessive allele are present.