Restriction maps:

Any double-stranded DNA will be cut through a variety of restriction enzymes which have variant recognition sequences.  Through  separating  the  restriction  measuring  and fragments their sizes through gel electrophoresis,  it is probable to deduce where on the DNA  molecule  every  restriction  enzyme  cuts.  The restriction map of the DNA molecule can be drawn showing the location of these cut sites (restriction sites) described in the figure. It is then simple to compare two DNA molecules (for instance, to examine the evolutionary relationship among two species) through looking at their restriction maps without the required to determine the nucleotide sequence of every DNA. Restriction maps are also very important experimentally during recombinant DNA work both to strategy where individual DNA molecules should best be cut and to monitor the progress of the experiment.

Figure: A typical restriction map of a DNA molecule. The cleavage sites of different restriction enzymes, indicated by letters, are shown. For example, E denotes sites where EcoRI cuts.