Q.In RNAi, genes are silenced using:

In RNA interference (RNAi), the silencing of a specific gene is achieved using double-stranded RNA (dsRNA). This dsRNA is complementary to the mRNA of the target gene. Once inside the cell, the dsRNA is processed into small interfering RNAs (siRNAs) by an enzyme called Dicer. These siRNAs then guide a protein complex to the complementary mRNA, leading to its degradation and thus preventing translation. …

RNA interference, or RNAi, is a fascinating natural mechanism that cells use to regulate gene expression. It was first observed in plants and later understood in detail through work on the nematode worm Caenorhabditis elegans, for which Andrew Fire and Craig Mello won the Nobel Prize in 2006. The core idea is that when a cell encounters double-stranded RNA (dsRNA) matching a specific gene's sequence, it actively destroys any messenger RNA (mRNA) from that gene, effectively "silencing" it.

The process works like this. The dsRNA is first chopped up by an enzyme called Dicer into small pieces called small interfering RNAs (siRNAs), each about 21-23 nucleotides long. These siRNAs then unwind, and one strand is loaded into a protein complex called RISC (RNA-induced silencing complex). The siRNA guides RISC to find any mRNA that has a complementary sequence. Once found, RISC cuts that mRNA, preventing it from being translated into protein. The result is that the gene's expression is shut down at the post-transcriptional level.

Method — match the trigger molecule to the silencing mechanism by definition

RNAi's defining feature (by name and mechanism) is that a DOUBLE-STRANDED RNA is what gets recognised and chopped into siRNAs — single-stranded RNA/DNA of either kind cannot trigger th …