Restriction fragment length polymorphism: Difference between revisions

Revision as of 10:54, 10 May 2016

Revision as of 21:02, 14 May 2016

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There are two common mechanisms by which the size of a particular restriction fragment can vary. In the first schematic, a small segment of the genome is being detected by a DNA probe (thicker line). In allele "A", the genome is cleaved by a restriction enzyme at three nearby sites (triangles), but only the rightmost fragment will be detected by the probe. In allele "a", restriction site 2 has been lost by a [[genetic mutation|mutation]], so the probe now detects the larger fused fragment running from sites 1 to 3. The second diagram shows how this fragment size variation would look on a Southern blot, and how each allele (two per individual) might be inherited in members of a family.

In the third schematic, the probe and restriction enzyme are chosen to detect a region of the genome that includes a variable [[Variablevariable number tandem repeats|VNTRrepeat]] segment (boxes). In allele "c" there are five repeats in the VNTR, and the probe detects a longer fragment between the two restriction sites. In allele "d" there are only two repeats in the VNTR, so the probe detects a shorter fragment between the same two restriction sites. Other genetic processes, such as [[Genetic insertion|insertions]], [[Genetic deletion|deletions]], [[Chromosomal translocation|translocations]], and [[Chromosomal inversion|inversions]], can also lead to RFLPs.

RFLP uses a much bigger sample of DNA than STR.