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 ?
We performed a second linkage mapping analysis with the Chr 10 QTL regressed out but did not find any additional QTL at the genome wide p < 0.
The presence of transposable elements--in particular, the association to commonly used molecular markers like microsatellites--may pose some technical challenges for linkage mapping, because transposable elements often facilitate unequal recombination (Lira & Simmons 1994).
Development of amplified fragment length polymorphism (AFLP) markers suitable for genetic linkage mapping of catfish.
Such subject groups are relatively easy to obtain, giving the candidate gene approach an important advantage over the linkage mapping approach, which requires the analysis of families with multiple affected members.
pleuronectes transcriptome will be useful for population genetics analysis and linkage mapping construction.
Characterization and linkage mapping of expressed sequence tags (ESTs) isolated from a subtracted cDNA library of Pacific whiteleg shrimp, Litopenaeus vannamei, injected with White spot syndrome virus.
Even though, linkage mapping is being used for gene mapping in crop plants, it is very costly, has low resolution and evaluates few alleles simultaneously in a relatively longer time scale (Flint- Garcia et al.
KEY WORDS: Litopenaeus vannamei, White Spot Syndrome Virus, WSSV, linkage mapping, expressed sequence tags, ESTs, ShrimpMap, myosin light chain, E-F hand motif, actin, ribosomal proteins
First announced in November 2003, the BeadStation 500G has been tested extensively at the University of California, Los Angeles (UCLA), where Nelson Freimer, MD, and his research team performed genetic linkage mapping analysis on 288 samples using Illumina's high-multiplex GoldenGate(TM) assay and Sentrix(R) Array of Arrays(TM) platforms, integral components of the BeadStation offering.
Molecular linkage mapping provides opportunities for plant breeders to practice marker-assisted selection (MAS) as they develop new cultivars.
With the introduction of this system, researchers can now perform a full range of integrated genotyping applications, including microsatellite or SNP-based linkage mapping, fine mapping of SNPs, and resequencing, on the same instrument.