Scientists who wish to clone genes of interest into bacterial plasmids utilize restriction enzymes, which cuts the target and vector DNA at specific sites. then DNA ligase is used to form covalent bonds between the resulting fragments to complete the recombinant DNA molecule.
Restriction enzymes (endonucleases) are enzymes which recognize specific target sequences (recognition sites) and will make a double-stranded cut in the DNA molecule at or near recognition sites. DNA ligase is an enzyme which uses ATP to link two DNA molecules if they have matching ends.