Restriction enzyme analysis:
The restriction endonuclease analysis of viral DNA fragments or DNA fingerprinting discovered in 1970s has revolutionized the study of viruses. Restriction endonucleases cut DNA molecule at specific sequences to produce a reproducible number of fragments in agarose gel electrophoresis for each DNA genome. The number and size of the fragments generated depend on the enzyme used and the frequency with which the specific cleavage sites are present in the DNA. This technique allows differentiation between the variants of the organisms and is a powerful tool for the study of infectious agents.