Introduction - Gene Regions
Once a gene has been located and cloned, genetic engineers usually need to modify it so that it expresses in a specific and desired way when inserted into the plant. The modification involves changing the sequences in the regions of the gene that control gene expression.
Genes have three regions, the promoter, coding region, and termination sequence.
The promoter turns the gene on. The coding region has the protein building information, and the termination sequence indicates the end of a gene.
The three regions of a gene. (Image by P. Hain)
The promoter and the coding region are the gene regions that are normally modified. Using special DNA modifying enzymes, geneticists can cut apart the gene regions, remove one of them, and replace it with another that will direct gene expression as desired. The gene is then considered recombinant DNA since it has a new combination of DNA. This part of the genetic engineering process can be very time consuming but also gives the genetic engineer a wide array of gene design options to try.