A restriction digest is a procedure used in molecular biology to prepare DNA for analysis or other processing.
[1] The resulting digested DNA is very often selectively amplified using polymerase chain reaction (PCR), making it more suitable for analytical techniques such as agarose gel electrophoresis, and chromatography.
Restriction enzymes specific to hundreds of distinct sequences have been identified and synthesized for sale to laboratories, and as a result, several potential "restriction sites" appear in almost any gene or locus of interest on any chromosome.
Furthermore, almost all artificial plasmids include a (often entirely synthetic) polylinker (also called "multiple cloning site") that contains dozens of restriction enzyme recognition sequences within a very short segment of DNA.
The gel is then subjected to an electric field, which draws the negatively charged DNA across it.