Bt Cotton MCQ - Practice Questions & Answers

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Insect Resistant Transgenic Plant - Bt Cotton is considered one of the most asked concept.
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Insect Resistant Transgenic Plant - Bt Cotton

Some strains of Bacillus thuringiensis (Bt) produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes).
B. thuringiensis forms protein crystals during a particular phase of their growth.
These crystals contain a toxic insecticidal protein.
The bacterium itself is not killed by the toxin because Bt toxin protein exists as inactive protoxins but once an insect ingests the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilises the crystals.
The activated toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis and eventually cause the death of the insect.
Specific Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into several crop plants such as cotton.
The choice of genes depends upon the crop and the targeted pest, as most Bt toxins are insect-group specific.
The toxin is coded by a gene named cry.
There are a number of them, for example:
- the proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms,
- cryIAb controls corn borer.