Applications Of Biotechnology

The correct answer is option (C): Cry I Ac and Cry II Ab
The cry genes encode the crystal protein (Bt toxin)that is toxic to some plant species. The cry genes are produced during the growth of Bacillus thuringiensis. The cry genes cry I Ac and cry II Ab, help in killing the cotton bollworms. The cry toxin has specific activity against the insects of the order Diptera, Coleoptera, and Lepidoptera. When the insect ingests these crystals, the alkaline medium provided by their digestive system denatures the insoluble crystal. This will be cut with proteases in the gut, which will further liberate toxins. The toxin will eventually form pores in the digestive tract and thus paralyze the insect.

Step 1: Understanding the Concept:
Genetic engineering involves manipulating the DNA of an organism to introduce new traits. Scientists prefer organisms that reproduce quickly and have simple genetic structures.
Step 2: Detailed Explanation:
Bacteria (especially \textit{E. coli}) are widely used because they grow rapidly, their genome is well-understood, and they contain plasmids (circular DNA) that can be easily manipulated to carry foreign genes, such as the gene for human insulin.
Step 3: Final Answer:
The correct option is (b).