Which of the following describes a recessive trait?

A recessive trait is characterized by its expression only when two copies of the recessive allele are present, which means the organism must inherit one recessive allele from each parent. In a genetic context, if an individual has one dominant and one recessive allele, the dominant allele will mask the effect of the recessive one, resulting in the dominant phenotype being expressed.

This is based on Mendelian genetics, where alleles can be dominant or recessive. The recessive trait does not show up in the phenotype—the observable characteristics—unless both alleles are recessive. Thus, the only scenario where the recessive trait will be manifest is when there are two recessive alleles present. If there is only one recessive allele present, it remains unexpressed due to the presence of the dominant allele, which reinforces the idea that a recessive trait requires the homozygous condition (two identical recessive alleles) for its expression.

In summary, the defining aspect of a recessive trait is its requirement for the presence of two recessive alleles to be expressed phenotypically.