Insertion of the DNA fragment into a vector

• A vector is used to transport DNA into a host cell, once the appropriate fragment has been cut and the promoter / terminator regions have been added.
• The most commonly used vector is a plasmid. Plasmids are circular lengths of DNA, found in bacteria, which often contain the genes for antibiotic resistance.
• Restriction endonucleases can be used at the antibiotic-resistance gene sites in a plasmid to break the plasmid loop.
• When using a vector, the restriction endonuclease used to cut out the DNA fragment must be the same as the one being used to break the plasmid loop. This way, the sticky ends of the opened-up plasmid are complementary to the sticky ends of the DNA fragment.
• When the DNA fragments with the complementary sticky ends are mixed with the opened up plasmids, they may become incorporated into them. This binding is fortified by the DNA ligase enzyme, forming permanent recombinant DNA.