Five events happen when a caterpillar eats Bt cotton…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Five events happen when a caterpillar eats Bt cotton. They are given here in a mixed order.
A. Pores form in the cells, the cells swell and burst.
B. The alkaline pH of the gut dissolves the crystals.
C. The active toxin binds to the surface of the midgut epithelial cells.
D. The caterpillar eats leaf tissue that holds the protoxin.
E. The protoxin is changed to the active toxin.
- Put the events in the right order.
- At which event does the toxin become active?
- Name the cells that are damaged.
Need a reminder? The key ideaShow
The soil bacterium Bacillus thuringiensis makes crystals of an inactive protoxin. In the alkaline gut of an insect, the crystals dissolve and the protoxin becomes the active toxin. It binds to the midgut cells, makes pores, and the cells swell and burst. The toxin gene is called cry. The genes cryIAc and cryIIAb control the cotton bollworms, and cryIAb controls the corn borer. Most Bt toxins act on one group of insects only.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) The caterpillar eats the plant (D). The alkaline gut dissolves the crystals (B). The protoxin becomes the active toxin (E). The toxin binds to the midgut cells (C). Pores form and the cells burst (A). The order is D, B, E, C, A.
Step 2. (b) At E, in the gut, after the crystals have dissolved.
Step 3. (c) The epithelial cells that line the midgut.
Answer: (a) D, B, E, C, A; (b) E; (c) the cells of the midgut lining.
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