Gel-electrophoresis pattern of a restriction digest. This gel shows the fragments produced by cleaving DNA from two viral strains (odd- vs. even-numbered lanes) with each of four restriction enzymes. These fragments were made fluorescent by staining the gel with ethidium bromide.

[Data from Carr et al., Emerging Infectious Diseases, www.cdc.gov/eid, 17(8), August 2011.]