An organism with two alleles that are exactly the same is called homozygous.

Here's a breakdown:

* Allele: A variation of a gene.

* Homozygous: Having two identical alleles for a particular trait.

* Heterozygous: Having two different alleles for a particular trait.

For example, if an organism has two copies of the allele for blue eyes, it would be homozygous for eye color.