Which term describes having two identical alleles for a gene?

The term that describes having two identical alleles for a gene is homozygous. This means that an individual has inherited the same version of a gene from both parents, whether it's the dominant or recessive allele. When an organism is homozygous for a trait, it tends to express that trait uniformly.

In contrast, being heterozygous refers to having two different alleles for a gene, which can lead to a blending or a dominance interaction in trait expression. Hemizygous pertains to a situation where only one allele is present in a diploid organism, often seen in males with X-linked traits where they have one X and one Y chromosome, lacking a second allele on the X chromosome. The term genotype represents the genetic makeup of an organism, including both homozygous and heterozygous configurations, but does not specifically indicate the equality of the alleles. Understanding these definitions clarifies the role that homozygosity plays in genetics and inheritance.