In RNA interference (RNAi) the genes are silenced using:

The correct answer is Option (2) → ds-RNA

Option (1) ds-DNA — Incorrect. Double-stranded DNA is the gene itself. RNAi does not act on the gene; it acts on the mRNA copied from it, and a DNA molecule is not what blocks that mRNA.

Option (2) ds-RNA — Correct. In RNAi a complementary double-stranded RNA stops a particular mRNA from being translated, so its protein is never made. In the tobacco plant, the nematode genes put in by Agrobacterium made both sense and anti-sense RNA. The two joined to form dsRNA, which silenced the nematode’s mRNA, and the parasite could not survive.

Option (3) ss-RNA — Incorrect. The mRNA is itself single-stranded. In RNAi the single-stranded mRNA is the target that gets silenced, not the tool that silences.

Option (4) ss-DNA — Incorrect. Single-stranded DNA, tagged with a radioactive molecule, is used as a probe to find a gene in molecular diagnosis. It plays no part in RNAi.

Note: A similar question was also asked in CUET (UG) 2023 on 23-06-2023 (Slot 3).

NCERT Extract:
Biotechnological Applications in Agriculture – …