What are the sources of dsRNA? Diagram the mechanisms by which dsRNAs are produced and processed into small RNAs.

Verified step by step guidance

1. Identify the sources of double-stranded RNA (dsRNA), which can include viral replication intermediates, transcription of inverted repeat sequences, and bidirectional transcription of overlapping genes.
2. Understand that dsRNA is recognized by the cellular machinery as a signal for RNA interference (RNAi) pathways, which are crucial for regulating gene expression and defending against viral infections.
3. Diagram the initial recognition of dsRNA by the enzyme Dicer, which cleaves the dsRNA into small interfering RNAs (siRNAs) or microRNAs (miRNAs), typically 20-25 nucleotides in length.
4. Illustrate the incorporation of these small RNAs into the RNA-induced silencing complex (RISC), where one strand of the small RNA (the guide strand) is retained and the other strand (the passenger strand) is degraded.
5. Show how the RISC, guided by the small RNA, binds to complementary mRNA targets, leading to mRNA degradation or translational repression, effectively silencing the gene expression.

Key Concepts

Double-stranded RNA (dsRNA)

Double-stranded RNA (dsRNA) is a type of RNA that consists of two complementary strands, similar to the structure of DNA. It is often produced during viral infections or as a byproduct of certain cellular processes. dsRNA plays a crucial role in the regulation of gene expression and the immune response, particularly in the context of RNA interference (RNAi).

RNA interference (RNAi)

RNA interference (RNAi) is a biological process in which small RNA molecules inhibit gene expression by targeting specific mRNA for degradation. This process is initiated by the presence of dsRNA, which is processed into small interfering RNAs (siRNAs) or microRNAs (miRNAs) by the enzyme Dicer. RNAi is a vital mechanism for regulating gene expression and defending against viral infections.

Dicer and RISC complex

Dicer is an enzyme that processes long dsRNA into short double-stranded fragments known as small interfering RNAs (siRNAs). These siRNAs are then incorporated into the RNA-induced silencing complex (RISC), which uses the siRNA as a guide to recognize and degrade complementary mRNA. This mechanism is essential for the post-transcriptional regulation of gene expression and the cellular response to dsRNA.