Q. Bt toxin is produced by a bacterium called Bacillus thuringiensis (Bt for short). These Bt toxin crystals contain a toxic insecticidal protein. The toxin is coded by a gene named cry which has many variants. Which one from the following produces a toxin that controls corn borer?

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Solution:

Bacillus thuringiensis (or Bt) is a soil-dwelling bacterium, commonly used as a biological pesticide. Many Bt strains produce crystal proteins that have insecticidal action. B.thuringiensis forms crystal proteins or Cry proteins, which are encoded by cry genes. The cry genes are mostly located on a plasmid. There are a number of them, for example, the proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms and that of cryIAb control corn borer.