Gene Silencing And Editing

dsRNA in RNAi:

1. Processed into siRNA by Dicer.
2. siRNA binds to RISC complex, guiding it to cleave complementary mRNA → blocks translation.

Translation of mRNA is the process by which a cell interprets the genetic code in messenger RNA (mRNA) to synthesize a corresponding protein. It occurs in the cytoplasm of the cell and is facilitated by ribosomes, which read the mRNA sequence and assemble the protein by linking amino acids in the correct order. This process is part of the overall gene expression process, following transcription, where DNA is transcribed into mRNA.

Not affected:

• (A) Transcription: Occurs in nucleus.
• (B) RNA transport: Unrelated to dsRNA.
• (D) Aminoacylation: tRNA charging process.

Correct Answer: (C) Translation of mRNA

Gene silencing refers to techniques used to reduce or eliminate the expression of a specific gene, typically by interfering with its messenger RNA (mRNA) transcript.

Let's analyze the options:

• Short interfering RNA (RNAi): RNA interference is a natural biological process where small RNA molecules regulate gene expression. In the context of gene silencing technology, synthetic short interfering RNAs (siRNAs) are introduced into cells. These siRNAs are designed to be complementary to the target mRNA sequence. They are incorporated into the RNA-induced silencing complex (RISC), which then finds and cleaves the target mRNA, or inhibits its translation, thereby silencing the gene. This is a valid method for gene silencing.
• Antisense RNA: Antisense technology uses short, synthetic single-stranded nucleic acid sequences (antisense oligonucleotides, which can be RNA or DNA) that are complementary to a specific region of the target mRNA. When the antisense molecule binds to the mRNA, it forms a duplex. This duplex can physically block the ribosome from translating the mRNA or can make the mRNA susceptible to degradation by cellular enzymes (like RNase H if a DNA-RNA hybrid is formed). This interference prevents protein production, thus silencing the gene. This is also a valid method for gene silencing.
• by Both A & B: Since both RNAi (using siRNA) and Antisense RNA are established methods used to achieve gene silencing by targeting mRNA, this option is correct.
• None of the above: This is incorrect because both A and B are valid methods.

Therefore, silencing of a gene could be achieved through the use of both Short interfering RNA (RNAi) and Antisense RNA.

RNA interference (RNAi) is a mechanism that regulates gene expression by specifically targeting and degrading mRNA molecules. It is mediated by small RNA molecules, particularly small interfering RNAs (siRNAs) or short hairpin RNAs (shRNAs), which are derived from longer dsRNA molecules.

In the RNAi process, the dsRNA molecule is introduced into the cell, which is then processed by an enzyme called Dicer into siRNAs or shRNAs. These small RNA molecules bind to the target mRNA sequence, typically through complementary base pairing, forming a RNA-induced silencing complex (RISC).

The RISC complex guides the degradation or inhibition of the target mRNA, preventing its translation into protein. The silencing of specific mRNA through RNAi is a powerful tool in molecular biology research for studying gene function and has potential applications in therapeutics.