How does RNAi “silence” a gene?

Verified step by step guidance

1. RNA interference (RNAi) is a biological process where RNA molecules inhibit gene expression or translation by neutralizing targeted mRNA molecules.
2. The process begins with the introduction of double-stranded RNA (dsRNA) into a cell, which is then recognized and cleaved by an enzyme called Dicer into small interfering RNAs (siRNAs).
3. These siRNAs are then incorporated into a protein complex known as the RNA-induced silencing complex (RISC).
4. Within the RISC, the siRNA is unwound, and the single-stranded RNA guides the complex to the complementary mRNA target.
5. The RISC then cleaves the mRNA, leading to its degradation and preventing it from being translated into a protein, effectively 'silencing' the gene.

Key Concepts

RNA Interference (RNAi)

RNA interference (RNAi) is a biological process in which RNA molecules inhibit gene expression or translation, effectively silencing specific genes. This mechanism is crucial for regulating gene activity and defending against viral infections. RNAi is initiated by the presence of double-stranded RNA (dsRNA), which is processed into small interfering RNAs (siRNAs) that guide the silencing machinery to target mRNA.

Small Interfering RNA (siRNA)

Small interfering RNA (siRNA) are short, double-stranded RNA molecules, typically 20-25 nucleotides in length, that play a key role in the RNAi pathway. Once incorporated into the RNA-induced silencing complex (RISC), siRNAs bind to complementary mRNA sequences, leading to mRNA degradation or inhibition of translation. This specificity allows for targeted gene silencing.

Gene Silencing Mechanism

The gene silencing mechanism involves the recognition and binding of siRNA to its complementary mRNA, which triggers the RISC to cleave the mRNA strand. This degradation prevents the mRNA from being translated into protein, effectively silencing the gene. This process is vital for regulating gene expression and can be harnessed for therapeutic applications, such as targeting disease-related genes.