Question

Answer the following questions:

• Explain how the process of RNA interference technology is used effectively to prevent infestation of the roots of tobacco plant by the nematode Meloidogyne incognita.
  OR
• Explain how more than a billion copies of a fragment of DNA are formed using the technique of PCR.

Hint:

RNA interference uses double-stranded RNA to silence genes, while PCR uses repeated cycles of heating and cooling to exponentially amplify DNA fragments.

Answer 1

1. RNA interference (RNAi) Technology:
   • In this method, specific genes responsible for nematode infestation are silenced.
   • The nematode Meloidogyne incognita affects tobacco plant roots.
   • To counter this, a DNA sequence producing both sense and antisense RNA strands for the nematode’s essential genes is introduced into the plant using Agrobacterium vectors.
   • These complementary RNA strands form double-stranded RNA (dsRNA) inside the host plant cells.
   • The dsRNA triggers the RNA interference (RNAi) mechanism, degrading the nematode’s specific mRNA.
   • As a result, the target gene is silenced, protecting tobacco plants from nematode attack.
2. Polymerase Chain Reaction (PCR) Process:
   • PCR is a technique to amplify a specific segment of DNA.
   • The process involves multiple cycles of:
     • Denaturation: Double-stranded DNA is heated to separate into single strands.
     • Annealing: Primers bind to the specific target sequences.
     • Extension: DNA polymerase extends primers to synthesize new DNA strands.
   • Each cycle doubles the DNA quantity.
   • Repeating this process for around 30 cycles results in over a billion copies of the desired DNA fragment.