the DNA at these points. The restriction enzymes do not cut through both strands of the DNA at the same point however; they leave overhangs known as sticky ends. Enzymes are also used to treat the host DNA, to open up a gap into which the target gene can be inserted. If the host DNA is incubated with the same restriction enzymes used to chop out the target gene, the sticky ends will be complementary to the sticky ends of the excised gene.
             The next step is ligation. This is the joining of the target gene with the host DNA.
             The target gene is placed into a vector; this is a section of DNA that is used to carry the target gene into the microbe. The most common vectors used are called plasmids. These are circular chains of DNA that occur naturally in bacteria. Although they are separate from the chromosomal DNA in the bacteria, the plasmids do replicate and express the proteins which they contain genes for. Incubating a mixture of the target gene
             ...