Read the following passage carefully and answer the given questions.
Insulin consists of two short polypeptide chains- chain A and chain B, that are linked together by disulphide bridges. Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans, coleopterans and dipterans. Bt toxin protein is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals. Transgenic animals that produce useful biological products can be created by the introduction of the portion of DNA (or genes) which codes for a particular product such as human protein (α-1-antitrypsin) used to treat emphysema. Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO). GM plants have been useful in many ways. Genetic modification has: (i) made crops more tolerant to abiotic stresses. (ii) reduced reliance on chemical pesticides (pest-resistant crops). (iii) helped to reduce post harvest losses. (iv) increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil). (v) enhanced nutritional value of food.
Which one of the following species is not killed by insecticidal protein produced by Bacillus thuringiensis?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Meloidegyne incognitia
Some strains of Bacillus thuringiensis make a toxic protein (Bt toxin) that kills certain insects. The passage names the groups: lepidopterans, coleopterans and dipterans. Each Bt toxin is specific to an insect group, so it does not harm other animals.
Option (1) Army worm — Killed by the Bt protein.
Option (2) Meloidegyne incognitia — Not killed by the Bt protein. It is a nematode (roundworm), not an insect. It infects the roots of tobacco plants. Tobacco is protected from it by RNA interference (RNAi), not by Bt toxin.
Option (3) Flies — Killed by the Bt protein.
Option (4) Beetles — Killed by the Bt protein.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Biotechnological Applications in Agriculture – “… A nematode Meloidegyne incognitia infects the roots of tobacco plants and causes a great reduction in yield.”
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).”
