Statement I: When a crop expresses a cry gene, it typically gains resistance against a group of insects.
Statement II: Cry proteins derived from Bacillus thuringiensis exhibit toxicity towards the larvae of specific insects.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Both statements I and II are correct.
Statement I: When a crop expresses a cry gene, it typically gains resistance against a group of insects. — True. The cry genes code for Bt toxins. Each toxin acts on one group of insects only, so the gene put into a crop is chosen to match the pest of that crop. The crop then resists that group of insects.
Statement II: Cry proteins derived from Bacillus thuringiensis exhibit toxicity towards the larvae of specific insects. — True. Cry proteins are the toxin proteins coded by cry genes. They kill certain insects, such as lepidopterans (bollworms, budworms), coleopterans (beetles) and dipterans (flies, mosquitoes). The toxin is inactive in the bacterium. In the alkaline gut of the insect larva it becomes active, makes pores in the gut cells and kills the larva.
NCERT Extract:
Bt Cotton – “Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). … Specific Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton (Figure 10.1). 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 cryIAc named cry. There are a number of them, for example, the proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms, that of cryIAb controls corn borer.”