RFLPs - Restriction Fragment Length Polymorphism Maps and Linkage of RFLP with Specific Genes

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Home >>Molecular Probes and Gene Libraries >> RFLPs - Restriction Fragment Length Polymorphism Maps and Linkage of RFLP with Specific Genes

	RFLPs - Restriction Fragment Length Polymorphism Maps and Linkage of RFLP with Specific Genes - RFLPs have been used to prepare chromosome maps in humans, mice, fruit fly, and in plants including maize, tomato, lettuce and rice. The use of Mendelian markers for genetic mapping is sometimes limited due to non availability of mutants. The list of markers can be extended by using molecular markers, which are examined in the form of RFLPs. Once a large number of RFLPs are available in a species, the parents, F1 and F2's can, be used to study their inheritance and linkage relationship and genetic linkage maps can be prepared. They have been assigned to specific chromosomes using monosomics in maize and efforts are being made to relate them with morphological and economic traits so that they can be used for practical plant breeding.
A difference in restriction maps between two individuals or a RFLP can be used as a genetic marker in much the same way as any other phenotypic marker. The polymorphism at the molecular level may be due to the presence or absence of a restriction site. The presence of an additional site will produce two fragments and its absence will produce only one fragment. Although, there may be linkage between a molecular marker and a phenotypic trait, the change in molecular map (restriction map) may not affect the phenotype. In order to study linkage relation between a molecular marker and a phenotypic marker, we may examine the restriction fragment patterns and the phenotypes of two parents that differ morphologically as well as for molecular markers.
By making crosses between two such parents, we can estimate the recombination frequencies between molecular markers and phenotypic markers using a test cross. In, we used a hypothetical example showing linkage of red mid white eyes with different molecular markers in Drosophila. It can be seen that as a result of recombination, in test cross, 15% progeny shows association of red eye with a molecular marker associated with white eye in the parent and vice versa. Therefore, it is concluded that restriction marker is 15 map units away from the marker eye colour, although it has no causal relation with eye colour. Such a linkage between molecular marker and phenotypic marker allows identification of genetic loci .It the molecular level. A tight linkage of such a molecular marker with disease resistance may also be recommended as a tool for identification of disease resistant cultivars in many of our crop plants and will be increasingly utilized in future. Molecular markers are also being used for selection of plants at the seedling stage for plant breeding purposes.

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