What term describes having two identical alleles of a gene?

The term that describes having two identical alleles of a gene is "homozygous." In genetics, an individual is classified as homozygous when they possess two copies of the same allele for a specific gene, which can be either dominant or recessive. This means that both alleles at a particular locus are the same, leading to a uniform genetic trait expression.

In contrast, a heterozygous individual has two different alleles at a gene locus, resulting in a combination of traits that can vary based on dominance. Hemizygous refers to having only one allele at a gene locus, usually applicable to genes on the X or Y chromosomes in males. Haploid describes a cell containing only one complete set of chromosomes, such as gametes (sperm or egg cells), rather than the condition of alleles present for specific genes. Thus, the concept of being homozygous is pivotal in understanding inheritance patterns and genetic variation.