| Restriction Fragment Length Polymorphism (RFLP)
Restriction fragment length analyses uses restriction enzymes (RE) to cut DNA at specific 4-6 bp recognition sites (Dowling et al. 1990). Sample DNA is cut (digested) with one or more RE’s and resulting fragments are separated according to molecular size using gel electrophoresis (Avise 1994). Molecular size standards are used to estimate fragment size. Ethidium bromide staining is used to reveal the fragments under UV (260 nm) light. Differences result from base substitutions, additions, deletions or sequence rearrangements within RE recognition sequences (Avise 1994). Restriction fragment length polymorphism (RFLP) is most suited to studies at the intraspecific level or among closely related taxa. Presence and absence of fragments resulting from changes in recognition sites are used identifying species or populations. 
Figure 1. Gel showing RFLP variation between SCN and SBCN using Fok I RE
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