Question

In RNAi, genes are silenced using

• A. ssDNA
• B. ssRNA
• C. dsDNA
• D. dsRNA

Answer 1

The correct option is D

dsRNA

The correct option is option D.

Explanation of the correct option:

1. As a form of cellular defence, RNAi is used by all eukaryotic species.
2. An enzyme known as dicer helps break up long double-stranded RNA into small fragments.
3. These fragments are called small interfering RNA or siRNA
4. The siRNAs are passed through the complex of RNA-induced silencing.
5. The RNA is activated and the duplex unwinds.
6. These complexes inhibit translation while promoting RNA breakdown.
7. The siRNA binds to the Argonaute protein and one of the double-strands is cut off.
8. The remaining strand binds the mRNA target sequences.
9. To control the target sequence, the Argonaute protein either cleaves the mRNA or gets the help of other factors.

Explanation of the incorrect options:

Option A:

1. Single-stranded DNA (ss) viruses are exceedingly common, infecting a wide range of hosts from all three domains of life, and are major pathogens.
2. The majority of ssDNA viruses have tiny genomes that reproduce through a rolling-circle-like mechanism that is initiated by a virus-encoded endonuclease.

Option B:

1. By co-opting host factors, ssRNA viruses can modify the host's gene expression and also defences.

Option C:

1. Double-stranded DNA is made up of two polynucleotide chains joined by hydrogen bonds at their nitrogenous bases.
2. Because the sugar-phosphate backbones are anti-parallel and the A-T and C-G base pairings are complimentary, one strand in this arrangement replicates the other.

Final Answer: In RNAi, genes are silenced using dsRNA.