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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



the state, inherent in every hybrid organism, in which homologous chromosomes carry different forms (alleles) of a given gene or differ in the arrangement of genes (structural heterozygosity).

The term “heterozygosity” was first introduced by the English geneticist W. Bateson in 1902. Heterozygosity is the result of the union of gametes of different genetic or structural makeup. Structural heterozygosity arises with the chromosomal rearrangement of one of the homologous chromosomes; it may be detected in meiosis or in mitosis. Heterozygosity is revealed by crossing a hybrid with its homozygous-recessive parental form. Heterozygosity, as a rule, is a consequence of the sexual process, but it can arise as a result of mutation (for example, in the homozygote AA, where one of the alleles has mutated: A→A’). The effect of harmful or lethal recessive alleles is suppressed in a heterozygote by the presence of the corresponding dominant allele and becomes apparent only with the transfer of the allele to a homozygous situation. Heterozygosity is widespread in natural populations and is apparently one of the reasons for hybrid vigor (heterosis). The masking action of the dominant alleles in heterozygosity allows the preservation and diffusion through a population of harmful recessive alleles, which should be unmasked in the course of breeding and selection as well as in making medical and genetic prognoses (for example, through evaluative testing of a stock by studying its progeny).


Brewbaker, G. L. Sel’skokhoziaistvennaia genetika. Moscow, 1966. (Translated from English.)
Lobashov, M. E. Genetika, 2nd ed. Leningrad, 1967.
Efroimson, V. P. Vvedenie v meditsinskuiu genetiku, 2nd. ed. Moscow, 1968.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
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This mutation was found in heterozygosis in one proband, a woman who presented 382 mg/dl of LDLc even after 3 months of treatment.
East and Hayes (1912) state: "The greater the degree of heterozygous condition the greater is the vigor of the resulting plant, and the decrease in vigor due to inbreeding lessens with decrease in heterozygosity and vanishes with isolation of a completely homozygous strain." Shull (1948) states: "In 1914, I proposed the word heterosis to replace the more cumbersome word 'heterozygosis' which had been found useful by a few geneticists of that time, myself among them." Knight (1948) defines heterozygosis as the state of being heterozygous; that is, formed from the union of gametes of dissimilar genetic constitution.
This fact is related to the very composition of the segregating population under evaluation, given that the parents that composed the crosses were divergent and possibly presented most of their loci in heterozygosis for the traits assessed.
[28] in compound heterozygosis with another known NPHS2 mutation in two nonrelated SRNS Chinese children.
Akodon cursor (ACU) presents variation in diploid numbers (2n = 14 to 16) due to a complex rearrangement involving chromosomes 1 and 3, in which pericentric inversions followed by a centric fusion gave rise to a karyotype with 2n = 15 when in heterozygosis or 2n = 14 when in homozygosis [6,8].
The null-activity CYP2C19*3 and CYP2C19*5 alleles were not present in any of the studied populations, and CYP2C19*4 was only present in heterozygosis in two subjects of the admixed population.
The heterozygosity of the five microsatellite markers in the present study was from 0.8702-0.9236 with an average heterozygosity of 0.8840 all of which have high heterozygosity thus belonging to high heterozygosis sites.
Individuals with 2n = 36 can only have 1 Rb homozygous fusion or both fusions in heterozygosis. Individuals with 2n = 33 and with 2n = 34 have extra fusions involving acrocentrics of different size (Fig.
Nevertheless, despite the fact that most of these frequent HLA-G variable sites are not within known regulatory elements, several lines of evidence indicate balancing selection acting on the HLA-G promoter found in several populations [6, 8, 9, 78,79], suggesting that divergent promoters have been maintained with high heterozygosis. This observation is probably related to a possible better fitness of individuals carrying both high- and low-expressing promoters.
The main goal of animal breeding studies on genetic diversity among sire groups is the identification of hybrid combinations with high heterozygosis to increase the possibility of recuperating the superior genotypes in the segregating generations (VIANA et al., 2000).
The literature reports that an increase in the platelet count, nystagmus, ataxia towards the right, dysmetria and motor deficit, sensory loss on the right side of the face eight days after cesarean section, cerebral MRI showing right cerebellar and median posterior bulbar infarction, color Doppler ultrasonography of the cerebral veins showing occlusion in the right vertebral artery, coagulation pattern analysis showing MTHTR gene and single prothrombin gene mutation heterozygosis could be various significant risk factors bringing on stroke during pregnancy.5