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Related to Heterozygosity: Loss of heterozygosity
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 It might be outdated or ideologically biased.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.
References in periodicals archive ?
The average observed heterozygosity (Ho) ranged from 0.391 to 0.678 (average 0.497), which are comparative lower than the expected heterozygosity (HE) that ranged from 0.582 to 0.860 (with an average of 0.725).
All the loci displayed higher observed heterozygosity for both breeds except OarFCB11.
The expected heterozygosity value was higher than the observed heterozygosity value in all populations studied.
Heterozygosity, effective number of alleles, and PIC were generally used to measure the level of polymorphic genetic markers and their application.
The cultured population (Ajanla) has a higher heterozygosity of 0.419 [+ or -] 0.133 than the wild (Asejire) with 0.387 [+ or -] 0.152.
The number of alleles per locus (k) ranged from 7.88 to 8.67; the expected heterozygosity (He), from 0.80 to 0.97; and the observed heterozygosity (Ho), from 0.24 to 0.26.
Observed heterozygosity ([H.sub.o]) varied from 0.224 (MaF214) to 0.776 (OarFCB128) with an average about 0.584 while the average expected heterozygosity ([H.sub.e], gene diversity) for all loci was 0.785 with variation between 0.765 (BM8125) and 0.807 (MaF36).
Whole exome sequencing (WES) performed on the patient and both parents at GeneDx (Gaithersburg, MD) revealed heterozygosity for a p.R921X variant [c.2761 C>T (p.Arg921Ter)] in exon 19 of NPR2 gene in the patient and the mother.
Genetic high-resolution melt curve analysis of a biopsy sample revealed compound C282Y/H63D heterozygosity, confirming a genetic defect in the donor tissue, which elicited hereditary hemochromatosis in a recipient without any known HFE mutation.
p.Trp12* (exon 1), p.Asn76Thr (exon 3), p.Ser673Argfs*6 (exon 14), p.Cys698Arg (exon 14), and c.4352+4A> C (intron 29) were each detected once in heterozygosity in 5 respective patients, and c.5714+1G>C was detected twice in two patients (1 in homozygosity, 1 in heterozygosity) and c.4352+1G>A (in three patients in heterozygosity).
The evaluation index of genetic diversity includes expected heterozygosity (He), observed heterozygosity (Ho) and polymorphic information content (PIC).
Conclusion: The three polymorphisms have a low heterozygosity rate in HB families from KP and FATA.