– obtained from bacterial cells where they act as an immune system, they digest foreign DNA molecules from viruses
– molecular scissors that cut DNA at a specific base-pair sequence (the recognition site)
– they scan DNA, stop at their recognition sites, then disrupt the phosphodiester bonds and the hydrogen bonds between nucleotides cutting a molecule of DNA into fragments
– blunt ends are fragment ends of a DNA molecule that are fully base paired (no overhang), resulting from cleavage by a restriction enzyme
– sticky ends fragment end of a DNA molecule with short single-stranded overhangs, resulting from cleavage by a restriction enzyme
DNA Ligase
– sticky ends can form hydrogen bonds between complementary base pairs, but the phosphodiester bonds must be reformed to stabilize the DNA molecule
– DNA ligase is an enzyme that reforms phosphodiester bonds joining DNA fragments together
