noun
Technical term in genetics for an individual with two identical alleles at a given locus.
この遺伝子座について、その個体はホモ接合体である。
For this gene locus, that individual is a homozygote.
ヘテロ接合体 (heterozygote) has two different alleles at a locus, while ホモ接合体 has two identical alleles.
From English 'homozygote', combining 'homo-' (same) and 'zygote', with 接合体 (zygote) used in Japanese genetics terminology.