The specific mRNA of the nematode is silenced by:

The correct answer is Option (3) → Double stranded RNA

A nematode (a small roundworm) attacks the roots of tobacco plants and lowers the yield. It was controlled by RNA interference (RNAi), a way of silencing a gene. Nematode-specific genes were put into the tobacco plant using Agrobacterium vectors. The plant made both sense and anti-sense RNA of these genes. The two RNAs are complementary, so they joined and formed double stranded RNA (dsRNA). This dsRNA started RNAi and silenced the specific mRNA of the nematode, so the parasite could not survive.

(1) DNA-protein interactions — Incorrect. Such interactions, like a repressor binding to DNA, control genes. Here the silencing works on the mRNA.

(2) Enzyme deficiency — Incorrect. This is the lack of an enzyme, as in ADA deficiency. It does not silence any mRNA.

(3) Double stranded RNA — Correct. The dsRNA starts RNAi and silences the nematode’s mRNA.

(4) Double stranded DNA — Incorrect. DNA is normally double stranded, and it does not silence mRNA. RNAi needs dsRNA.

NCERT Extract:
Biotechnological Applications in Agriculture – …