Summary - Gene Regions

  • Gene design allows genetic engineers to modify a gene so that once inside a plant, it expresses in a desired way.
  • The 3 gene regions are:
    1. Promoter - Turns the gene on and specifies when, where in the plant, and how much protein to produce.
    2. Coding Region - Encodes the actual protein to be produced.
    3. Termination Sequence - Signals the end of the gene on a chromosome.
  • Promoters
    1. 35S - Originated from the Cauliflower Mosaic Virus, results in expression of the gene in all cells of the plant all the time.
    2. PEP Carboxylase - Originated from a photosynthetic enzyme, results in expression of the gene in actively photosynthesizing (green) tissues only. Expression will decrease towards the end of the season when the plant begins to die.
  • Bt coding regions
    1. Cry1A(b) - Kills ECB by binding to a receptor site in the midgut causing a water imbalance which ruptures the midgut.
    2. Cry1A(c) - DNA code is slightly different from the Cry 1A(b) coding regions, but kills the ECB in the same way.
    3. Cry9c - DNA code is moderately different from both the Cry1A(b) and Cry1A(c) coding regions. Kills the ECB by binding to a different receptor site in the midgut.
  • If resistance develops to one of the coding regions, a coding region with a different 'mode of action' may still be lethal to the population. An example would be using the Cry9c coding region which encodes a protein that binds to a different receptor site in the ECB midgut.