Which one of the following is used during 'RNA i' process, to silence the desired gene ?

The correct option/answer is dsRNA (double-stranded RNA).

Step-by-Step Explanation:

1. Understanding RNA Interference (RNAi):
RNA interference (RNAi) is a biological mechanism used by eukaryotic cells to regulate gene expression and defend against viral infections. It functions by silencing specific messenger RNA (mRNA) molecules, thereby preventing them from being translated into proteins.

2. The Role of Double-Stranded RNA (dsRNA):
The RNAi process is initiated by the presence of double-stranded RNA (dsRNA) molecules inside the cell. These dsRNA molecules can originate from viral replication, transposon activity, or can be introduced artificially for research and therapeutic purposes.

3. Mechanism of Silencing:
Inside the cell, the dsRNA is recognized and cleaved by an enzyme called Dicer into short fragments (approximately 21 to 23 nucleotides long) known as small interfering RNAs (siRNAs).
These siRNAs are then loaded into a multi-protein complex called the RNA-induced silencing complex (RISC). RISC unwinds the siRNA, keeping one strand (the guide strand) while degrading the other (the passenger strand).
The guide strand directs RISC to bind to a complementary target mRNA. Once bound, the catalytic component of RISC cleaves the target mRNA, leading to its degradation. As a result, the translation of the target gene is blocked, effectively silencing it.

4. Why other options are incorrect:
• dsDNA (Double-stranded DNA) and rDNA (Recombinant DNA): These are DNA forms and do not directly initiate the post-transcriptional silencing mechanism of RNAi in the cytoplasm.
• DNA polymerase: This is an enzyme responsible for synthesizing new DNA strands during DNA replication, not for silencing genes in the RNAi pathway.