homozygous

American  

[hoh-muh-zahy-guhs, hom-uh-] / ˌhoʊ məˈzaɪ gəs, ˌhɒm ə- /

Also homozygotic

adjective

Biology.

1. having identical pairs of genes for any given pair of hereditary characteristics.

2. of or relating to a homozygote.

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homozygous British  

/ -ˈzɪɡ-, ˌhɒm-, ˌhəʊməʊˈzaɪɡəs /

adjective

1. genetics (of an organism) having identical alleles for any one gene Compare heterozygous

   these two fruit flies are homozygous for red eye colour

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homozygous Scientific  

/ hō′mō-zī′gəs /

1. Relating to a cell that has two identical alleles for a particular trait at corresponding positions on homologous chromosomes.

2. Compare heterozygous

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Other Word Forms

• homozygosity
  noun
• homozygously
  adverb

Etymology

Origin of homozygous

1900–05; homo- + Greek -zygos; see zygo-, -ous

Explanation

If you're homozygous, you’ve got a pair of matching alleles, which are the two genes that control a particular trait. If both your alleles that determine blood type are O, you're homozygous — and you've got type O blood. The Greek root homo- means "same," and a zygote is a cell created when two gametes — a sperm and an egg, in humans — come together. The zygote gets half its genetic material from each parent, one allele in the pair from each. If the eye color allele you inherit from your mother and the one you get from your father are both for blue eyes, then you’re homozygous for that trait (and you have blue eyes).

Example Sentences

This has enriched rare functional variation, including recessive disorders and homozygous loss-of-function mutations, or “human knockouts.”

From The Wall Street Journal • Mar. 12, 2026

In Romito 2, researchers found a homozygous mutation in the NPR2 gene, which plays a key role in bone development.

From Science Daily • Feb. 17, 2026

An inheritance pattern in which an allele is only lethal in the homozygous form and in which the heterozygote may be normal or have some altered non-lethal phenotype is referred to as recessive lethal.

From Textbooks • Jun. 9, 2022

Only 2 rabbits in the second generation produce offspring, and both of these are homozygous dominant.

From Textbooks • Jan. 1, 2015

There, between graphs of “Disease Specific Infant Mortality” and a description of “the homozygous state of Garrodian inborn errors,” was the photograph of Henrietta with her hands on her hips.

From "The Immortal Life of Henrietta Lacks" by Rebecca Skloot