Explain how restriction endonucleases are used to form recombinant DNA plasmids.

Endonucleases cut DNA at palindromic sites producing 'sticky ends'. The endonuclease cuts the plasmid DNA and the DNA to be inserted at the same palindromic site. The sticky ends of the plasmid DNA and the insert DNA are complimentary and form hydrogen bonds. DNA ligase sticks the DNA together to form a recombinant DNA plasmid.