What does homozygosity mean?
Homozygosity is the condition in which an individual carries two identical copies of a gene or another genetic locus. It is the counterpart of heterozygosity, in which the two copies carry different alleles. The word is used most often in genetics and population biology, either for the condition at a particular locus or for the overall degree of homozygosity within a population. High homozygosity can be associated with reduced genetic variation and may arise in small or isolated populations, although the term itself does not identify a single cause. Researchers also use it when studying inherited disease, selective breeding, conservation, and the genetic relationships among individuals. The vocabulary is necessarily technical rather than everyday, but it expresses an important distinction in the study of inheritance: matching alleles do not contribute diversity at that locus, whereas differing alleles do.
nounThe state of being homozygous, in which the two copies of a gene or other genetic locus in an individual carry the same allele. The term can also refer to the degree to which this condition occurs in a population.
- The condition of being homozygous: having two identical copies of a gene or other genetic locus within an individual.
- The degree to which individuals in a population are homozygous at one or more genetic loci.
"The study found unusually high homozygosity in the isolated population."
"Homozygosity at the disease-associated locus may increase the likelihood that an affected allele is expressed."
"Population geneticists measured homozygosity to assess genetic variation among the island's descendants."
The plural is grammatically standard but uncommon, especially outside technical literature; authors often prefer the singular mass noun when discussing a general condition.
"The study compared homozygosities across several isolated populations."
Homozygosity means the two copies of a gene match; its genetic opposite is heterozygosity.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does homozygosity come from?
Homozygosity combines the Greek roots homo-, meaning “same,” and zygosity, referring to the pairing of chromosomes or inherited alleles. Its formation follows the related terms homozygote and homozygous, with the suffix -ity turning the condition into a noun. The contrasting term heterozygosity uses the Greek prefix hetero-, meaning “different,” and shares the same second root.
How homozygosity is actually used
This is primarily a formal scientific term used in genetics, population biology, breeding, and conservation genetics. It is especially common in research discussions of genetic variation, inbreeding, and relatedness; the plural is uncommon in general writing.
Easily confused with homozygosity
Homozygosity means that the two copies of a genetic locus carry the same allele, whereas heterozygosity means that they carry different alleles.