Complementary ds RNA which prevents translation is formed in ________.

Question

Prepp Team · Accepted Answer

Understanding dsRNA and Translation Prevention

The question asks about a specific biological process where complementary double-stranded RNA (dsRNA) is formed and prevents the translation of messenger RNA (mRNA) into proteins. This mechanism is a crucial part of gene regulation in many organisms.

Analyzing the Options

Let's look at each option to determine which process involves the formation of complementary dsRNA that blocks translation.

PCR (Polymerase Chain Reaction): PCR is a laboratory technique used to amplify specific DNA sequences. It involves DNA primers, DNA polymerase, and nucleotides, but not the formation of dsRNA to prevent translation.
RNA interference (RNAi): RNA interference is a biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules. This process involves short dsRNA molecules like small interfering RNAs (siRNAs) or microRNAs (miRNAs). These molecules guide a complex (like the RNA-induced silencing complex or RISC) that either degrades the target mRNA or blocks its translation. This perfectly matches the description in the question.
Gene therapy: Gene therapy is a broad approach to treating diseases by modifying gene expression. It can involve various methods, including introducing functional genes, editing genes, or using techniques like RNA interference to silence specific genes. While RNAi can be used *as a tool* within gene therapy, the process of forming complementary dsRNA to prevent translation *is* RNA interference itself, not the overarching term 'gene therapy'.
ELISA (Enzyme-Linked Immunosorbent Assay): ELISA is a test used to detect and quantify substances like peptides, proteins, antibodies, and hormones. It is an immunological technique and does not involve the formation of dsRNA or the prevention of translation.

The Mechanism of RNA Interference

RNA interference (RNAi) is a natural mechanism for gene silencing. It starts with the presence of dsRNA (either endogenous like pri-miRNA or exogenous like viral RNA or experimentally introduced dsRNA). This dsRNA is processed by enzymes like Dicer into shorter fragments, typically 20-25 base pairs long, called small interfering RNAs (siRNAs) or mature microRNAs (miRNAs).

These short dsRNA fragments are then loaded into a protein complex called the RNA-induced silencing complex (RISC). Within the RISC, one strand of the dsRNA is discarded, leaving a single-stranded guide RNA (either a single-stranded siRNA or one strand of a miRNA duplex). This guide RNA is complementary to a specific target mRNA sequence.

The RISC complex, guided by the single-stranded RNA, binds to the complementary sequence on the target mRNA. Binding can lead to:

mRNA degradation: If the complementarity is perfect or near-perfect (common with siRNAs), the RISC complex (often containing the enzyme Argonaute) cleaves and degrades the target mRNA.
Translational repression: If the complementarity is imperfect (more common with miRNAs in animals), the RISC complex blocks ribosomes from translating the mRNA into protein, effectively preventing protein synthesis from that mRNA molecule.

Thus, the formation of complementary dsRNA leading to the prevention of translation (or mRNA degradation) is the defining characteristic of RNA interference.

Process	Involves dsRNA preventing translation?	Primary function
PCR	No	Amplify DNA
RNA interference	Yes	Gene silencing (via mRNA degradation or translational repression)
Gene therapy	Can use RNAi, but not the specific process itself	Treating disease by genetic modification
ELISA	No	Detecting and quantifying substances (immunological test)

Conclusion on dsRNA and Translation Blockage

Based on the analysis, the process where complementary dsRNA is formed and specifically prevents translation is RNA interference.

Revision Table: Key Concepts in Molecular Biology

Term	Definition	Relevance to Question
dsRNA	Double-stranded RNA molecule.	Key component involved in initiating RNA interference.
Translation	Process where mRNA is used as a template to synthesize protein.	The biological process that is inhibited in RNA interference.
mRNA	Messenger RNA; carries genetic information from DNA to ribosomes for protein synthesis.	The target molecule that is degraded or translationally repressed in RNA interference.
RNA interference (RNAi)	Biological process where RNA molecules inhibit gene expression, often by targeting mRNA.	The correct process where complementary dsRNA prevents translation.
Gene Silencing	Regulation of gene expression by blocking transcription or translation. RNAi is a major mechanism.	The outcome achieved by RNA interference.

Additional Information: Types of RNA in Gene Silencing

There are two main types of small RNAs involved in the RNA interference pathway:

siRNAs (small interfering RNAs): Typically derived from longer exogenous or perfectly complementary endogenous dsRNA. They usually lead to cleavage and degradation of target mRNA due to perfect or near-perfect complementarity. Often involved in defense against viruses and transposable elements.
miRNAs (microRNAs): Typically derived from endogenous hairpin-shaped RNA precursors (pri-miRNAs). They usually bind to target mRNA with imperfect complementarity, leading primarily to translational repression or sometimes mRNA degradation. Involved in regulating development and cellular processes.

Both siRNAs and miRNAs function by forming a complex with Argonaute proteins within the RISC complex, allowing them to identify and interact with target mRNA molecules based on sequence complementarity, ultimately impacting protein synthesis via translational repression or mRNA degradation.