Restriction fragment

[1] 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.

Restriction fragments can be analyzed using techniques such as gel electrophoresis or used in recombinant DNA technology.

[2] In recombinant DNA technology, specific restriction endonucleases are used that will isolate a particular gene and cleave the sugar phosphate backbones at different points (retaining symmetry), so that the double-stranded restriction fragments have single-stranded ends.

These short extensions, called sticky ends, can form hydrogen bonded base pairs with complementary sticky ends on any other DNA cut with the same enzyme (such as a bacterial plasmid).

In agarose gel electrophoresis, the restriction fragments yield a band pattern characteristic of the original DNA molecule and restriction enzyme used, for example the relatively small DNA molecules of viruses and plasmids can be identified simply by their restriction fragment patterns.