What does it mean if an allele is recessive?

An allele is considered recessive when its trait is only expressed in the phenotype when an individual carries two copies of that allele, meaning both alleles received from each parent are recessive. This occurs because the dominant allele can mask the expression of the recessive allele when they are present together (one dominant and one recessive). For instance, in a genetic trait governed by two alleles, if one is dominant and the other is recessive, the dominant trait will be the one that is observed in the phenotype of a heterozygous individual. Only when an individual possesses two recessive alleles (homozygous recessive) will the recessive trait be expressed. Therefore, an allele being labeled as recessive signifies that its associated phenotype is not visible unless it is paired with another recessive allele.

This understanding clarifies why the other choices do not accurately describe a recessive allele: the first option inaccurately specifies that it is always expressed; the second option incorrectly suggests that a recessive allele can be expressed when paired with a dominant one; and the last option mistakenly limits the expression of the recessive allele to only males, which is not true, as recessive alleles can be expressed in both sexes under the right genetic