DNA cloning is a molecular biology technique used to make identical copies of a piece of DNA. During cloning, restriction enzymes are used to "cut" out a piece of DNA, then ligase is used to "paste" the DNA into plasmids. Next, the plasmids are taken up by bacteria (usually E. coli). The plasmids are replicated inside the bacteria, and the bacteria also replicate, making many copies of the original piece of DNA.