Amplified Fragment Length Polymorphism. A hybrid ofRFLPandRAPDtechniques. Genomic DNA is cut with restriction enzymes, as in RFLP. Typically, two different restriction enzymes are used. The idea is to produce a large number of fragments. Some of the fragments are selectively amplified with PCR using "random" primers, as in RAPD. The primers are not really random, however. Specific oligonucleotide "adapters" (these are complementary to the restriction sites) of 25-30 bp are ligated to the restricted DNA fragments. The primers are complementary to these adapters. However, the primers vary at their 3'-end, such that they will amplify only a subset of the restricted DNA fragments. Typically, a moderate-to-high number of bands will be observed, most of which may be monomorphic. Polymorphic bands are identified as in RAPD analysis. Polymorphic bands can even be excised from the gel and sequenced. This allows for specific PCR primers to be developed, if necessary. AFLPs have typically been used to study variation among individuals of a species, most commonly for producing genetic maps (and in trying to find genes responsible for certain traits). They have received limited attention as tools in systematics, perhaps because the method is relatively labor intensive when compared with other methods. The power of AFLP is based upon the molecular genetic variations that exist between closely related species, varieties, or cultivars. These variations in DNA sequence are exploited by the AFLP technology such that "fingerprints" of particular genotypes can be routinely generated. These "fingerprints" are simply RFLPs visualized by selective PCR amplification of DNA restriction fragments.
More about AFLP technology inPubMed.
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