Question

Arrange the steps in the correct order as they are involved in RNA interference (RNAi):
(A) Formation of small interfering RNAs (siRNAs)
(B) Activation of RNase III-like enzyme Dicer
(C) Inactivation of target RNA
(D) Formation of RISC complex
Choose the correct answer from the options given below:

• A. (A), (B), (C), (D)
• B. (A), (C), (B), (D)
• C. (B), (A), (C), (D)
• D. (C), (B), (D), (A)

Hint:

Remember RNAi as a sequential process: Dicer activation → siRNA formation → mRNA targeting → RISC-mediated degradation.

Answer 1

The Correct Option is C

RNA interference (RNAi) is a cellular process that regulates gene expression by degrading or inhibiting target mRNA. The steps are:
1. Activation of RNase III-like enzyme Dicer (B): The RNAi pathway starts with Dicer activation. This enzyme processes long double-stranded RNA (dsRNA) into small interfering RNAs (siRNAs).
2. Formation of small interfering RNAs (siRNAs) (A): Dicer cleaves dsRNA into siRNAs. These are approximately 21–23 nucleotides long with 2-nucleotide overhangs at their 3' ends.
3. Inactivation of target RNA (C): siRNAs are incorporated into the RNA-induced silencing complex (RISC). Here, they guide the complex to complementary mRNA sequences.
4. Formation of RISC complex (D): The RISC complex, which contains Argonaute proteins, binds the siRNAs. This binding facilitates target mRNA recognition and cleavage, leading to its inactivation.