Any double-stranded DNA will be cut by a variety of restriction enzymes that have different recognition sequences. By separating the restriction fragments and measuring their sizes by gel electrophoresis, it is possible to deduce where on the DNA molecule each restriction enzyme cuts. A restriction map of the DNA molecule can be drawn showing the location of these cut sites (restriction sites). It is then easy to compare two DNA molecules (for example, to examine the evolutionary relationship between two species) by looking at their restriction maps without the need to determine the nucleotide sequence of each DNA. Restriction maps are also important experimentally during recombinant DNA work, both to plan where individual DNA molecules should best be cut and to monitor the progress of the experiment.
