DNA restriction endonucleases, enzymes that cleave DNA at specific sites, have been talked about primarily in connection with recombinant DNA technology.
Surprisingly, then, one of their first medical applications is not in the synthesis of insulin or human growth hormone, but as a tool for investigating the epidemiology of herpesvirus outbreaks in hospitals.
Restriction endonucleases split DNA at specific nucleotide sequences, yielding each time the same unique set of DNA fragments from a given DNA. If the DNA is radioactively labeled, the fragments may be separated on an agarose slab in an electric field and visualized by exposing the slab to roentgenographic film (figure, next page).
Analysis of DNA from more than 80 different strains of herpesvirus in the laboratory of Bernard Roizman, ScD, professor of microbiology at the University of Chicago, has shown that any two epidemiologically distinct strains of herpesvirus can be distinguished by the fragments produced from