In molecular biology, restriction sites, or restriction recognition sites, are regions of a DNA molecule containing specific (4-8 in length
Function
For example, the common restriction enzyme
EcoRI recognizes the palindromic sequence GAATTC and cuts between the G and the A on both the top and bottom strands. This leaves an overhang (an end-portion of a
DNA strand with no attached complement) known as a sticky end
on each end of AATT (AATTC, i.e. TTAAC). The overhang can then be used to ligate in (see
DNA ligase) a piece of DNA with a complementary overhang (another EcoRI-cut piece, for example).
Some restriction enzymes cut DNA at a restriction site in a manner which leaves no overhang, called a blunt end.
Applications
Restriction sites can be used for multiple applications in molecular biology such as identifying restriction fragment length polymorphisms (
). Restriction sites are also important consideration to be aware of when designing
.
Databases
Several databases exist for restriction sites and enzymes, of which the largest noncommercial database is REBASE.
Recently, it has been shown that statistically significant
nullomers (i.e. short absent motifs which are highly expected to exist) in virus genomes are restriction sites indicating that viruses have probably got rid of these motifs to facilitate invasion of bacterial hosts.
contains a comprehensive catalogue of minimal absent motifs many of which might potentially be not-yet-known restriction motifs.
See also
-
List of restriction enzyme cutting sites
