Question

Answer either option-(A) or (B): (A)

• Name the two genes encoding for the Bt toxin protein used in biotechnology for the control of cotton bollworms.
• How does the expression of Bt toxin gene in Bt cotton plant help in providing resistance to cotton bollworms? Explain.

OR (B)

• Explain the given methods of introducing the alien DNA in the host cells:
• (I) Biolistics
• (II) Microinjection
• How is E. coli made 'competent' to take up a recombinant plasmid or DNA?

Hint:

Biolistics is especially useful for plant genetic transformation, while microinjection is ideal for animal cells. Bt cotton expresses bacterial genes to provide in-built pest resistance.

Answer 1

(A)

1. The two genes encoding Bt toxin proteins are:
   • cry IAc
   • cry IIAb
2. In Bt cotton, the Bt toxin gene is expressed in plant tissues. When the cotton bollworm feeds on these tissues, the toxin is activated in the insect's alkaline gut, creating pores in the gut epithelium, leading to swelling, cell lysis, and death of the insect — thereby providing resistance to cotton bollworms.

OR (B)

1. • Biolistics (Gene gun method): Tiny gold or tungsten particles coated with the desired DNA are shot into plant cells at high velocity to deliver foreign DNA.
   • Microinjection: The foreign DNA is directly injected into the nucleus or cytoplasm of animal cells using a fine glass needle.
2. E. coli cells are made 'competent' by treating them with a solution of calcium chloride followed by a brief heat shock at \(42^\circ \text{C}\). This creates temporary pores in the bacterial cell membrane, allowing recombinant plasmids or DNA to enter.