A farmer in one district grows cotton, and a farmer in another district grows maize…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A farmer in one district grows cotton, and a farmer in another district grows maize. Both lose crops to caterpillars.
- Which cry genes could protect the cotton from its bollworms?
- Which cry gene could protect the maize from the corn borer?
- Why would the gene for the corn borer not be the first choice for the cotton?
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 genes cryIAc and cryIIAb.
Step 2. (b) The gene cryIAb.
Step 3. (c) The choice of the gene depends on the crop and on the targeted pest, because most Bt toxins are insect-group specific. NCERT lists cryIAb for the corn borer, not for the cotton bollworms.
Answer: (a) cryIAc and cryIIAb; (b) cryIAb; (c) toxins act on particular insects, so the gene must fit the pest.
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