Restriction enzymes

endodeoxyribonulceases that bind to specific base sequences and

break phosphodiester bonds on both strands of DNA

For example the restriction enzyme EcoR1 will bind to the base sequence below and break the phsophodiester bonds between G and A

DNAs with the ECOR1 specific DNA sequence at different places will be cut into fragments of different lengths

DNAs of different sizes can be separated on

agarose gels