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 ?
An AFLP-based genetic linkage map of channel catfish (Ictalurus punctatus) constructed by using an interspecific hybrid resource family.
It's very difficult to do genetic linkage analysis for a complex trait like endometriosis, he said.
The scientists set out to make a first, sketchy version of a road atlas -- known as a genetic linkage map -- of the rat genome.
ABSTRACT Genetic linkage maps were constructed for the noble scallop Chlamys nobilis Reeve on the basis of 373 amplified fragment length polymorphisms (AFLPs) and 9 microsatellite markers.
This textbook for advanced students of statistical genetics, genetic epidemiology, and human molecular genetics who are interested in gene mapping discusses genetic linkage and association analysis with an emphasis on conducting genome-wide studies into complex behaviors and diseases.
These microsatellite markers will be useful in constructing a genetic linkage map for the duck and a comparative mapping with the chicken can also provide a valuable tool for studies related to biodiversity and population genetics in this duck species.
SAN DIEGO -- A large genetic linkage study has pinpointed the major histocompatibility complex on the short arm of chromosome 6 as the key genetic player in multiple sclerosis.
Genetic linkage and association studies have identified many chromosomal regions and quantitative trait loci (QTL) associated with complex phenotypes related to alcohol induced behaviors and/or alcoholism.
If a relationship existed between certain genetic markers and a given phenotype--for example, if a variant of a marker occurred more commonly in family members with the phenotype than would be expected by chance--this served as evidence of genetic linkage.
Their blood test, called a genetic linkage analysis, yielded accurate positive or negative results for more than two-thirds of the volunteers but was inconclusive for the remaining participants (SN: 2/16/91, p.
Combining new targeted next generation sequencing technologies with the traditional genetic linkage analysis enabled the efficient capture and high quality sequencing of the region, and led to the discovery of the disease causing mutation at a speed which was unimaginable a few years ago.
After sifting through a massive database and scanning the entire genome for more than 317,000 single nucleotide polymorphisms (SNPs), scientists discovered four genes with robust evidence of genetic linkage to lupus and nine additional genes with promising evidence of linkage to the disease.