Genetic Linkage

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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.


References in periodicals archive ?
Table 1: The number of polymorphic fragments and mapped fragments generated by each of 71 PstI+3/MseI+3 primer combinations in the development of the genetic linkage maps of Phalaenopsis '462' x Phalaenopsis '20'
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.
Order correlations increased considerably with regard to those obtained with herds without any genetic linkage even though they did not exceed 19% for cows and 43% for progenies (Table 4).
Researchers determine the influence of genetic factors on development of alcohol dependence and/or habitual smoking using family studies, genetic linkage analyses, and candidate gene association studies.
Dense genetic linkage maps of three Popidus species (Populus deltoides, P.
A genetic linkage map consisting of 343 RFLP, STS, and RAPD markers was constructed based on a subset (90) of the [F.
None of the new articles by itself constitutes clear genetic linkage to manic depression," asserts Elliot S.
The book begins with fascinating accounts of the history of dementia and dementia research, includes risk factor and genetic linkage research, and ends with chapters on health care and social policy that look beyond dementia and dependency.
However, new windows are rapidly being discovered through genetic linkage studies.
In genetic linkage studies it is necessary to secure the cooperation of multiple family members.
Genetic linkage studies are also being conducted to determine whether there is an underlying genetic basis for the Marfan syndrome, but results have been inconclusive (Schwartz et al.