Sticky ends

For this method, the cuts leave sticky ends: short stretches of unpaired bases at the ends of the DNA. Using the same enzyme gives the gene fragment and the opened plasmid matching sticky ends. Complementary bases on those ends can pair, positioning the gene in the gap in the plasmid.

Many restriction endonucleases make staggered cuts. These leave short single-stranded overhangs called sticky ends. The exposed bases in one sticky end can pair with complementary bases in a matching sticky end.