Question

Which one of the following statements is wrong in relation to transgenic Bt cotton plant?
A.Crop yield loss due to attack by Bacillus thuringiensis bacterium is reduced
B.Crop yield loss due to attack by lepidopteran insect pests is reduced
C.The use of chemical insecticides in the cotton field is minimized
D.Better quality cotton is produced

Answer 1

In Bt cotton Bt toxin has been used as a biological insecticide. The Bacillus thuringiensis is a common soil bacterium which produces a protein toxin that kills certain insects. The toxin is a crystal cry protein .

Complete answer:
- Cry proteins are toxic to larvae of insects like lepidopteran ,bollworm, beetles etc.
-The cry proteins exist as inactive protoxins and get converted into active toxin when ingested by the insect as the alkaline pH of the gut solubilizes the crystals.
-The activated toxin binds to the surface of epithelial cells of the midgut and creates pores.
-This causes swelling and lysis of cells leading to the death of insects (larva).
-The gene encoding Cry protein are called Cry gene
-The genes (cry genes ) encoding this protein are isolated from the bacterium and incorporated into several crop plant like cotton
-The proteins encoded by the cry gene Cry I Ac and Cry II Ab control cotton bollworms

So, the correct answer is D. Better quality cotton is produced.

Note:
The other examples include transgenic tobacco plant , tomato plant , potato plant .
The resistant gene reduces the crop yield loss due to attack by insects as result there is minimal use of insecticides.