RAS question
Bt cotton in India contains a gene from:
Correct answer: (A) Bacillus thuringiensis (a bacterium).
Bt cotton in India contains a Bt gene from Bacillus thuringiensis, a soil bacterium.
Explanation
Bt cotton is a transgenic cotton crop in which a Bt gene is inserted through genetic engineering. The PIB note explains that Bt stands for Bacillus thuringiensis, a soil bacterium that synthesises a crystal, or Cry, protein. In the insect gut, this protein breaks down and releases a toxin that kills the insect. Bt cotton contains a cry gene from Bacillus thuringiensis, producing Bt toxin, or Cry protein, that is toxic to bollworm larvae. Because the inserted gene comes from this bacterium and enables the cotton plant to produce its own pest-resistance toxin, the answer is Bacillus thuringiensis, not another plant, fungus or virus.
Why the other options are wrong
- (B) A fungus is wrong because the Bt gene source is Bacillus thuringiensis, a soil bacterium.
- (C) Another cotton variety is wrong because Bt cotton gets its pest-resistance gene through genetic engineering from an unrelated bacterium, not from cotton germplasm.
- (D) A virus is wrong because the Bt gene is tied to Bacillus thuringiensis and Cry protein production, with no viral source involved in the stated mechanism.
Concept
This tests the biotechnology part of Science and Technology: transgenic crops, inserted genes and pest resistance. It recurs in RAS because Bt cotton is India's standard example for linking genetic engineering with agriculture and biosafety.