The first stage of making recombinant DNA is to select a DNA strand to insert into the vector. The vector is an independent DNA molecule that scientists use only as a vessel to transfer new genetic material into another cell. The DNA strand that the scientist chooses to inject into the vector depends on what type of cell would be most appropriate for the respective scientific project, but the strands are usually from a bacteria cell or a human gene.
The purpose of the second stage is to prepare the vector for the recombinant formation process. This step involves cutting a piece of DNA with a restriction enzyme, ligating the DNA strand and inserting the strand into the vector with DNA ligase. Usually the insert also contains a definitive marker to enable scientists to more-easily distinguish and identify the recombinant molecules during the transformation. Many different markers exist, and each marker produces different effects. Thus, scientists can select a marker that is appropriate for the particular study being conducted.
The final stage entails the scientist inserting the vector into a host cell that has been carefully prepared to accept the foreign DNA. The host cell can be a bacteria cell such as E. coli. As the recombinant DNA is formed, the scientist incubates the vector and the host DNA together in what is known as the transformation process. By using the markers, the scientist can identify which cells have taken up the foreign DNA.
The transformation method refers to forming recombinant DNA by using a bacteria cell -- E. coli -- as a host cell. However, other methods of forming recombinant DNA use the same steps but do not use bacteria cells for host cells. For instance, nonbacterial transformation features the same steps as the transformation method but with a nonbacterial cell serving as the host cell. Human cells are typically used for genetic engineering or cloning research projects. Furthermore, phage introduction, or the transfection process, is an equivalent of the transformation method, except a phage is used as the host cell instead of bacteria.