Restriction fragment

A restriction fragment is a DNA fragment resulting from the cutting of a DNA strand by a restriction enzyme (restriction endonucleases), a process called restriction. Each restriction enzyme is highly specific, recognising a particular short DNA sequence, or restriction site, and cutting both DNA strands at specific points within this site. Most restriction sites are palindromic, (the sequence of nucleotides is the same on both strands when read in the 5' to 3' direction), and are four to eight nucleotides long. Many cuts are made by one restriction enzyme because of the chance repetition of these sequences in a long DNA molecule, yielding a set of restriction fragments. A particular DNA molecule will always yield the same set of restriction fragments when exposed to the same restriction enzyme. Restriction fragments can be analyzed using techniques such as gel electrophoresis or used in recombinant DNA technology.