In reference to Bt cotton, select the correct statement(s) :
(A) The alkaline pH of an insect gut solubilises the crystals of Bt toxin
(B) The acidic pH of an insect gut solubilises the crystals of Bt toxin
(C) The Bt toxin does not kill the tobacco budworm
(D) Specific Bt toxin genes were isolated from Bacillus thuringiensis
Choose the correct answer from the options given below :
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A) and (D) only
(A) The alkaline pH of an insect gut solubilises the crystals of Bt toxin — True.
(B) The acidic pH of an insect gut solubilises the crystals of Bt toxin — False. The pH is alkaline.
(C) The Bt toxin does not kill the tobacco budworm — False. It kills lepidopterans such as the tobacco budworm.
(D) Specific Bt toxin genes were isolated from Bacillus thuringiensis — True.
NCERT Extract:
Biotechnological Applications in Agriculture – “… 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). B. thuringiensis forms protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein. … Actually, the Bt toxin protein exist as inactive protoxins but once an insect ingest the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals. The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually cause death of the insect.”