An organism whose alleles for traits are identical is called homozygous.

Here's a breakdown:

* Alleles: Different versions of a gene. For example, a gene for eye color might have an allele for brown eyes and an allele for blue eyes.

* Homozygous: Having two identical alleles for a particular trait. For instance, someone with two alleles for brown eyes would be homozygous for brown eyes.

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