In order for a recessive trait to be expressed, what must a person inherit?

The expression of a recessive trait requires that an individual inherits two recessive alleles for that particular trait, one from each parent. This means that for the recessive trait to be phenotypically observed, there cannot be a dominant allele present. If only one recessive allele is inherited, and a dominant allele is present as well, the dominant trait will be expressed instead.

In genetic terms, traits are often represented by letters; for instance, "A" might represent a dominant allele, while "a" represents a recessive allele. The only genotype that results in the expression of the recessive trait is "aa," which consists of two recessive alleles. This is why the inheritance of two recessive genes is necessary for the trait to manifest in the individual.