Using a combination of restriction enzymes some of which are specific to DNA modifications, the technique can be used to visualize differences in methylation levels across the genome of a given organism.
The radiation produced by the radioactive labeling will cause the film to be exposed wherever the restriction fragments have migrated during electrophoresis.
For example, human and mouse DNA will produce distinctly different patterns when treated with the same combination of enzymes.
These finished auto-rads can be examined against each other, revealing any changes in gene expression that lead to visual differences in the film.
RLGS becomes useful when doing whole-genome scans, and can effectively do the work of thousands of polymerase chain reactions at once.