Which term describes a variant of a trait that can be expressed only when two copies are present (recessive)?

Which term describes a variant of a trait that can be expressed only when two copies are present (recessive)?

• A. Recessive Trait/Allele
• B. Dominant Trait/Allele
• C. Codominant
• D. Incomplete Dominance

Answer: (A)

A recessive allele is a version of a gene that only shows up in the phenotype when both copies are present. If an individual has at least one dominant allele, the dominant trait is typically expressed, masking the recessive one. Only when both alleles are recessive (homozygous recessive) does the recessive trait appear. The other terms describe different inheritance patterns. A dominant allele can express its phenotype with just one copy. Codominance means both alleles contribute to the phenotype in a heterozygote (like AB blood type), not hidden unless two recessive copies are present. Incomplete dominance yields an intermediate phenotype in the heterozygote (such as red and white blending to pink), which isn’t about being expressed only when two copies exist.

A recessive allele is a version of a gene that only shows up in the phenotype when both copies are present. If an individual has at least one dominant allele, the dominant trait is typically expressed, masking the recessive one. Only when both alleles are recessive (homozygous recessive) does the recessive trait appear.

The other terms describe different inheritance patterns. A dominant allele can express its phenotype with just one copy. Codominance means both alleles contribute to the phenotype in a heterozygote (like AB blood type), not hidden unless two recessive copies are present. Incomplete dominance yields an intermediate phenotype in the heterozygote (such as red and white blending to pink), which isn’t about being expressed only when two copies exist.