What does the term "recessive allele" mean?

• A. An allele that is always expressed
• B. An allele that is masked by a dominant allele
• C. An allele that causes mutation
• D. An allele that is never inherited

Answer: (B)

The term "recessive allele" refers to an allele that is masked by a dominant allele when both are present in an individual’s genotype. This means that if an individual carries one dominant allele and one recessive allele for a particular trait, only the dominant trait will be expressed in the phenotype. The recessive allele can only manifest its effect when an individual inherits two copies of it, one from each parent. This characteristic is fundamental to understanding basic inheritance patterns in genetics, as it explains why some traits may not appear in the offspring even if the alleles are present in the parental generation.

In contrast, an allele that is always expressed would likely be a dominant allele, and the notion that a recessive allele causes mutation or is never inherited does not align with the established understanding of genetics. Recessive alleles can be inherited but typically remain unexpressed in the presence of dominant alleles.