Read the passage and answer the following questions:
Genetic modification (GM) has been utilised to create custom-designed plants that serve as alternative resources for industries, producing starches, fuels, and pharmaceuticals. Biotechnology in agriculture has numerous applications, one of which involves developing pest-resistant plants to reduce the reliance on chemical pesticides. This is achieved by introducing the Bt toxin gene from the bacterium Bacillus thuringiensis (Bt) into plants, creating what is known as a bio-pesticide. Notable examples include Bt cotton, Bt corn, rice, tomato, potato, and soybean. Bt toxin is a naturally occurring insecticidal protein produced by certain strains of Bacillus thuringiensis. During a specific phase of their growth, these bacteria form protein crystals containing toxic substances. These crystals harbour inactive protoxins, which, when activated, become lethal to targeted insects. Different Bt toxin genes, such as cryIAc and cryIIAb, have been isolated and introduced into various crop plants, depending on the crop and the specific pests targeted, as Bt toxins are often insect-group specific. By incorporating these genes, plants gain inherent resistance to insects without the need for synthetic insecticides. This advancement in biotechnology has significant implications for sustainable and eco-friendly agricultural practices.
What is the significance of Bt toxin genes being insect-group-specific?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → They target specific pests without affecting other insects.
The passage states that genes are chosen “depending on the crop and the specific pests targeted, as Bt toxins are often insect-group specific”.
A toxin that is insect-group specific acts only on one group of insects. So a crop carrying such a gene is protected against its own pests, while other insects are not harmed. This is why the gene is matched to the pest of each crop.
Option (1) They can only be used in certain climates. — Incorrect. The specificity is about which insects the toxin acts on. It has no link with the climate in which the crop is grown.
Option (2) They target specific pests without affecting other insects. — Correct. Being insect-group specific means the toxin acts on the targeted pests only and leaves other insects unaffected.
Option (3) They enhance plant growth only in certain soil types. — Incorrect. Bt toxin genes give protection against insects. They do not make plants grow better, and soil type has nothing to do with them.
Option (4) They increase crop yield irrespective of pest presence. — Incorrect. A Bt gene raises the yield by saving the crop from its pests. Where the pest is absent, the gene has nothing to act on, so it cannot raise the yield on its own.