Restriction fragment length polymorphism denotes that a single restriction enzyme produces fragments of different lengths from the same stretch of genomic DNA of different strains of a species or from different related species. RFLPs are detected as follows: i. Large molecular weight genomic DNA is isolated from several strains or related species; ii. The fragments in these digests are separated through electrophoresis iii. These 'DNAs are then digested with a selected restriction enzyme iv. Exposed to a suitably radio-labelled appropriate DNA probe under conditions favouring DNA: DNA hybridization v. The resulting gel lanes are transferred and fixed to a suitable solid support and vi. The free probes are removed vii. The fragments to which the probe has hybridized are detected by filming them as distinct bands on a suitable photofilm through autoradiography. -triyambak.org