Hemizygosity


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Hemizygosity

 

the state in which one or several genes are unpaired (have no allelic partners), such as the (“sex-linked”) genes of the sex chromosomes in individuals of heterogametic sex. For example, if individuals of homogametic sex have genotype XAXa and those of heterogametic sex have genotype XAY they will produce, respectively, gametes XA, Xa, and XAY. Random union of these gametes will produce four types of individuals: XAXA, XAXa,XAY, and XaY. Of these, the second and fourth will be carriers of a alleles, but the a allele will manifest itself only in the fourth (hemizygous) individual, since there is no dominant partner. Hemizygosity may appear also as a result of chromosomal rearrangement. A number of sex-linked hereditary diseases, such as hemophilia and color blindness (caused by recessive sex-linked genes), are manifested in humans and animals as a result of hemizygosity. The principle of hemizygosity is also used in selective plant breeding by obtaining monosomes (organisms with a single unpaired chromosome) for determination of the genetic composition of chromosomes.

References in periodicals archive ?
Fetal genotyping for inheritance of both Rh C and Rh E has been routinely performed by using maternal plasma and should therefore be used in such cases where hemizygosity has been defined.
Both homozygosity and hemizygosity of c.1398+2T>A in the CYP11B2 gene would be compatible with the clinical diagnosis of primary hypoaldosteronism in this patient.
X-linked hemizygosity also has an impact under selective sweeps insofar as recessive advantageous mutations are fixed more rapidly than their autosomal counterparts, which means that, under selective sweeps, we expect to see a reduction of variation at loci with equivalent recombination rates on the X relative to autosomes.
Haplodiploids may provide new insights concerning the genetic basis of reproductive isolation, as well as Haldane's rule because of male hemizygosity.
Because of hemizygosity in males, we directly phased the maternal haplotypes of the DMD region.
The former condition would indicate hemizygosity and the latter homozygosity for the transgene(s).
In Drosophila, the X chromosome may contribute proportionately more to male traits than is indicated by its size, due to hemizygosity. Both these features should be borne in mind when evaluating the variance components for male life-history traits that are reported in this paper, or when comparing them to estimates obtained by different experimental designs.
Because sample CPSA was the only sample from a male patient, the lower sequencing depth in the OTC gene can be explained by the patient's hemizygosity for this X-linked gene.
Seeds collected from each plant were sown on media containing kanamycin to determine homozygosity or hemizygosity of [R.sub.1] plants.
Hemizygosity of the region containing the G365R site resulting from a large deletion, an inversion, uniparental disomy (genomic imprinting), or a de novo mutation may explain the pedigree.