Step 3 : Gene Design
Gene design relies upon another major discovery. This was the 'One gene One enzyme' Theory first proposed by George W. Beadle and Edward L. Tatum in the 1940's. Discoveries made during their research laid the groundwork for the theory that a single gene stores the information that directs the cell in how to produce a single enzyme (protein). Therefore, there is a single gene that controls the production of the Bt protein. It is called the Bt gene.
Once a gene has been cloned, genetic engineers begin the third step, designing the gene to work once inside a different organism. This is done in a test tube by cutting the gene apart with enzymes and replacing certain regions.
Replacing existing promoter with new promoter. (Image by P. Hain)
The first Bt gene released was designed to produce a level of Bt protein lethal to European corn borer and to only produce the Bt protein in green tissues of the corn plant, (stems, leaves, etc.). Later, Bt genes were designed to produce the lethal level of protein in all tissues of a corn plant, (leaves, stems, tassel, ear, roots, etc.).