Genetic Linkage


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Related to Genetic Linkage: genetic map, Complete linkage

Genetic Linkage

 

the joint transfer of two or more genes from parents to offspring. Genetic linkage occurs because such genes reside on the same chromosome, that is, they belong to the same linkage group and therefore cannot be accidentally recom-bined in meiosis, which occurs in the inheritance of genes residing on different chromosomes.

Genetic linkage was discovered in 1906 by the English geneticists W. Bateson and R. Punnett, who discovered in experiments on the crossing of plants the tendency of some genes to transfer together, thus violating the law of the independent combination of traits. This tendency was correctly explained by T. H. Morgan and his associates, who discovered a similar phenomenon in their study of inherited traits in the fruit fly (Drosophila).

Genetic linkage is measured by the frequency at which crossover gametes or spores are formed by a heterozygote on jointly transferring genes. In these gametes or spores, the genes occur in new combinations rather than in the original combinations, owing to the crossing-over of those parts of the homologous chromosomes bearing the genes. In some bacteria, another measure of genetic linkage is the frequency of joint transmission by inheritance of various genes in conjugation, genetic transformation, and transduction. The extent of genetic linkage may vary among the sexes: it is generally greater in the heterogametic sex. Genetic linkage may even be complete, without crossing-over, in one of the sexes, for example, in male Drosophila or in female Asiatic silkworms (Bombyx morí). The extent of genetic linkage may also vary with the age of the parents and with temperature. In addition, it may vary in the presence of chromosomal rearrangement or of mutant genes that influence the extent of genetic linkage.

S. M. GERSHENZON

References in periodicals archive ?
In this study, the first genetic linkage map of the blood clam was constructed based on 50 newly developed SSR markers and 534 polymorphic loci identified from 65 AFLP primer combinations among 109 Fl progeny of a full-sib family, as a basic infrastructure for the genetic improvement of blood clam.
When the COGA investigators compared genetic markers among sibling pairs in which both siblings met the COGA or lCD-10 criteria for alcohol dependence, they identified one DNA region (i.e., a locus) on chromosome 1 that showed genetic linkage with the "alcohol dependence" phenotype (Reich et al.
In conclusion, these microsatellite markers will be useful in construction of a duck genetic linkage map.
JoinMap[R] 3.0, Software for the calculation of genetic linkage maps.
Because the data presented in the previous section suggested some interaction of vulnerability factors for alcoholism and depression, the COGA investigators performed genetic linkage analyses using DNA samples from sibling pairs with the AAD, AorD, and DEP phenotypes in order to identify chromosomal regions linked to these phenotypes.
Genetic linkage maps are powerful research tools for the study of many organisms (Dib et al.
Genetic linkage studies already recruit participants for biologic analysis who also have social and cultural contrasts useful for ethnographic analysis.
As a result, the investigators can directly test for both genetic linkage and association between a gene of interest and the presence of alcohol dependence and habitual smoking.
Possible explanations for such increased mortality include higher accident rates (either naturally or because tools, machinery and even traffic patterns are designed for the convenience of right-handed people) or some genetic linkage with life-shortening prenatal or immune disorders.
The 10 newly developed microsatellites will have value to discriminate between Mytilus species, to support studies of introgression and hybridization and to strengthen and improve the available genetic linkage map.
The researchers conducted a genetic linkage analysis of the families and identified chromosomal regions that could contain genes that influence the development of BPD.
Accordingly, the objectives of this study were to (i) construct a genetic linkage map of the Texas bluegrass genome and (ii) identify molecular markers linked to the dioecy locus.