Which is the correct expression of a heterozygous genotype for a recessive genetic disorder?. a A aa Aa

Aa

Explanation: Alleles can be dominant or recessive. A dominant allele is one which has the ability to manifest itself outwardly in the presence of a recessive allele. A dominant allele is usually written in upper case such as A, T, B.

A recessive allele is one which cannot express itself in the presence of a dominant allele. It is usually written in lower case such as a, t, b. A heterozygous allele has one dominant and one recessive allele, for example Aa, Tt, Bb.