Bt toxins: proteins and their functions

Discussion: Does race matter in cancer research and treatment?

I. Introduction to the GM plant debate

A. The ultimate source of most of our cellular energy is light, which is converted

to food by plants (and also algae and photosynthetic prokaryotes)

B. Traditional genetic modification of plants

C. Genetically engineered plants

Frontline/Nova video: Harvest of Fear

II. Bt toxin

A. Bacillus thuringiensis

B. Cry proteins

C. What are proteins?

C. Mechanism of Cry protein cell toxicity

D. Cry proteins as pesticides

Study Questions:

1. How can a corn be made to produce its own pesticide?

2. What is the major difference between plants genetically modified by traditional and genetic engineering methods?

3. What is Bacillus thuringiensis? When does it express the Cry proteins?

4. What aspects of Cry protein structure do you think make its toxicity so specific to restricted groups of insects?

5. How could changing one or a few amino acids in a protein affect that proteins function?

6. What is the effect of Cry proteins on insect gut epithelial cells?

7. Both Cry toxins and Ras are proteins, why do they have different shapes and functions?

Powerpoint below