Question

what does the notation rr mean to geneticists?
heterozygous alleles
homozygous alleles
dominant alleles
recessive alleles

Explanation:

In genetics, alleles are alternative forms of a gene. When an organism has two different alleles for a gene (one dominant - represented by a capital letter and one recessive - represented by a lowercase letter like Rr), it is heterozygous. Homozygous means having two identical alleles (RR or rr). Dominant alleles are always expressed when present (like R), and recessive alleles are only expressed when there are two copies (rr).

Answer:

A. heterozygous alleles