What is a dominant trait?

• A. Trait that is always expressed in the phenotype
• B. Trait that is inherited only from the mother
• C. Trait that masks another trait
• D. Trait that recessive

Answer: (D)

Dominant trait describes the form that shows up when at least one dominant allele is present. It can mask the effect of the other allele (the recessive one) in a heterozygous individual, so the dominant phenotype is what you see even if one allele is recessive. For example, if being polled (hornless) is dominant to having horns, an animal with one polled allele and one horn allele will be polled, while only animals with two recessive horn alleles will be horned. The idea isn’t that dominance means “always expressed” or that it’s inherited from the mother or that it’s recessive; dominance is about which trait appears in the presence of both alleles.