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.
Which of the following pairs of a Bt toxin gene and the pest controlled by its protein is correctly matched?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → cryIAc – Cotton bollworm
Bt toxins are proteins coded by cry genes of Bacillus thuringiensis. Most of them act on one group of insects only, so the gene put into a crop is chosen to suit its pest. The book pairs the genes with their pests: cryIAc and cryIIAb control the cotton bollworms, while cryIAb controls the corn borer.
Option (1) cryIAb – Cotton bollworm — Incorrect. The protein of cryIAb controls the corn borer, not the cotton bollworm.
Option (2) cryIIAb – Corn borer — Incorrect. The protein of cryIIAb controls the cotton bollworms, along with that of cryIAc. It is not the gene named for the corn borer.
Option (3) cryIAc – Cotton bollworm — Correct. The protein encoded by cryIAc controls the cotton bollworms, which is why this gene has been put into Bt cotton.
Option (4) cryIAc – Corn borer — Incorrect. cryIAc is a cotton bollworm gene. The corn borer is controlled by the protein of cryIAb.
NCERT Extract:
Biotechnological Applications in Agriculture – “… 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.”