Question

A researcher introduces double-stranded RNA into a culture of mammalian cells. The double-stranded RNA corresponds to a region of a protein-coding gene of interest. How may the introduced RNA affect gene expression in these cells?

Answer 1

Introducing double-stranded RNA into mammalian cells can initiate RNA interference, leading to the degradation of complementary mRNA and subsequent downregulation of the target protein synthesis, thus affecting gene expression.

Step-by-step explanation:

Effects of Double-Stranded RNA on Mammalian Gene Expression

When double-stranded RNA (dsRNA) corresponding to a specific protein-coding gene is introduced into mammalian cells, it can trigger the process of RNA interference (RNAi). This occurs as the enzyme DICER attaches to the dsRNA and cleaves it into short fragments. A single strand from these fragments is then incorporated into the RNA-induced silencing complex (RISC). The RISC searches for and binds to an mRNA that is complementary to the RNA fragment. If a match is found, the mRNA is targeted for degradation, effectively silencing the gene from which the mRNA was transcribed. This leads to a decrease or complete cessation in the production of the protein coded by the gene, impacting gene expression in the cells.

The RNAi pathway is a critical regulatory mechanism in cells, used not only for developmental processes but also as a defense against viruses. Upon the introduction of siRNA or miRNA, the RISC complex can either cleave perfectly matched mRNA or inhibit translation if the miRNA is not fully complementary. This post-transcriptional regulation is an important tool in controlling gene expression and is leveraged in research and therapeutic interventions.

Answer 2

Double stranded RNA may affect gene expression negatively

Step-by-step explanation:

Double stranded RNA are molecules that can affect negatively the gene expression by the fact that this kind of molecule can be complementary to others RNA molecules, or also to DNA regions on the genome. Therefore, introducing such molecules in mammalian cells can inactivate the transcription of a specific gene by the fact that those molecules could block regions of the genome that code for a gene or by connecting to some RNA molecules by similarity. Such mechanisms will reduce the production (or expression) of a given protein in these cells.