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noun, plural: homozygotes

A nucleus, cell or organism where the alleles for a particular gene on each chromosome are identical


A cell or an individual may be classified based on zygosity (i.e. the degree of similarity or the dissimilarity of the DNA sequences in specific coding segments, or genes, on the homologous chromosomes). A cell or an organism may be homozygous, heterozygous, hemizygous, or nullizygous. An organism, a cell, or a nucleus that is homozygous is one in which the alleles located on the loci of homologous chromosomes are the same or identical. Such organism or cell is also called a homozygote.

Diploid (2n) organisms, such as humans, possess two sets of chromosomes. One set comes from the mother and another set from the father. In humans, the egg cell bears 23 chromosomes and the sperm cell also has 23. During fertilization, the union of these two gametes results in a zygote with 46 chromosomes. Each maternal chromosome has a corresponding paternal chromosome to match with based on their loci. Each pair of chromosomes is referred to as homologous chromosomes. When the alleles in the homologous chromosomes are the same, that individual is referred to as a homozygote.

Homozygotes are true breeding organisms since the trait in question can be held constant as they produce the same phenotypic result.

Word origin: Greek homo ("same") + zygote


See also:

Related form(s):

  • homozygous (adjective, of, or pertaining to homozygosity or a homozygote)