In molecular biology, restriction fragment length polymorphism (RFLP) is a technique that as the direct identification of many disease genes and mutations ) has replaced the need for RFLP disease linkage analysis (see SNP genotyping) . When people refer to restriction fragment length polymorphisms, also known as RFLPs, or SNPs, single nucleotide polymorphisms, these are just different. RFLPs and SNPs can be the basis for linkage maps and are useful for establishing parent-progeny relationships. Recombination frequency.
The explanation is that a given restriction site is not always found in all individuals. The absence of a site is usually caused by a single nucleotide difference that is most likely biologically neutral. Hence, for example, if a probe binds a 2- kb fragment in individual A of a haploid species and it binds a fragment of 2. Geneticists were surprised to discover that RFLPs are quite common in populations and that a large proportion of probes will detect one. RFLPs are identified by a rather hit-or-miss method of hybridizing panels of randomly cloned genomic fragments to genomic restriction digests of several different individuals in a family or a population.
The significance of RFLPs is threefold. Although at first the locus of the RFLP is not necessarily known, as more and more RFLPs are found, they can be mapped in relation to gene loci and in relation to other RFLP loci, and their positions gradually saturate the genetic map. The RFLPs are not biologically significant in most cases, but they can be used to map interesting genes and act as positions from which these genes can be cloned by positional cloning.
Second, in an extension of mapping analysis, RFLP alleles morphs can be used as diagnostic tools. For example, in a family with a record of a certain disease, if it can be established that the people who have the disease also carry a specific allele of an RFLP, then this fact suggests not only that the RFLP locus is linked to the disease gene locusbut furthermore that the specific RFLP allele is in cis arrangement with the disease allele.
Hence the RFLP allele becomes a diagnostic marker for the disease, and this information can be used in genetic counseling.
Third, RFLPs can be used to measure genetic divergence between different populations or related species. The restriction-site difference is effectively a DNA difference, so a measure of the total number of RFLP differences represents a measure of genetic difference.
Hence RFLPs are important in studies of evolution. The RFLPs can be mapped relative to one another or to genes of known phenotypic expression. Progeny are tested for all three loci.
RFLP mapping - An Introduction to Genetic Analysis - NCBI Bookshelf
Adenine requirement is tested by inoculating strains on medium lacking adenine, and the RFLP alleles are tested by probing with the relevant probes. Recombinant frequencies are calculated in the usual way.
It would imply that the restriction marker lies so close to the mutant gene that it is never separated from it by recombination. The identification of such a marker has two important consequences: It may offer a diagnostic procedure for detecting the disease. Some of the human diseases that are genetically well characterized but ill defined in molecular terms cannot be easily diagnosed.
Restriction fragment length polymorphism - Wikipedia
If a restriction marker is reliably linked to the phenotype, then its presence can be used to diagnose the disease. It may lead to isolation of the gene. The restriction marker must lie relatively near the gene on the genetic map if the two loci rarely or never recombine. Although "relatively near" in genetic terms can be a substantial distance in terms of base pairs of DNA, nonetheless it provides a starting point from which we can proceed along the DNA to the gene itself.
The frequent occurrence of SNPs in the human genome makes them useful for genetic mapping. This should allow rapid localization of new disease genes by locating them between the nearest SNPs Sachidanandam et al. On the same principle, RFLP mapping has been in use for some time.
Restriction fragment length polymorphism
Once an RFLP has been assigned to a linkage group, it can be placed on the genetic map. RFLP mapping in man and mouse has led to the construction of linkage maps for both genomes.
Any unknown site can be tested for linkage to these sites and by this means rapidly placed on to the map Donis-Keller et al. The particular combination of sites found in a specific region is called a haplotype, a genotype in miniature.
The concept now has been extended to describe the particular combination of alleles or restriction sites or any other genetic marker present in some defined area of the genome.