A
restriction enzyme (also
restriction endonuclease) is an
enzyme that cuts double-stranded
DNA. The position where the enzyme cuts the DNA is determined by a sequence of
nucleotides that differs for each enzyme. Cuts can either result in
blunt or sticky ends. Restriction enzymes allow the splicing of DNA from one source (or species) into another. Note that the DNA sequences recognised by these enzymes are palindromic-the sequence on one strand reads the same in the opposite direction on the complementary strand.
Original sequence
GTCAGCCTGAGTCTGATGCTGAC
CAGTCGGACTCAGACTACGACTG
Blunt ends
GTCAGCCTG AGTCTGATGCTGAC
CAGTCGGAC TCAGACTACGACTG
Sticky ends
GTCAGCCTG AGTCTGATGCTGAC
CAGTCGGACTCAGAC TACGACTG
Today, restriction enzymes are an essential tool (like scissors) in molecular biology.