Final Answer:
RNA interference (RNAi) is a regulatory mechanism in cells that controls gene expression by degrading or inhibiting the translation of specific mRNA molecules. It plays a crucial role in various biological processes, including development, immunity, and maintenance of genome stability. The two major classes of RNAi are small interfering RNA (siRNA) and microRNA (miRNA).
Step-by-step explanation:
RNA Interference (RNAi): RNA interference is a biological process that regulates gene expression. It involves the introduction of double-stranded RNA (dsRNA) into a cell, leading to the degradation or inhibition of the translation of specific mRNA molecules.
Two Major Classes:
Small Interfering RNA (siRNA): These are short RNA molecules, typically 21-23 nucleotides in length, that are involved in the degradation of specific mRNA molecules. SiRNAs are often exogenously introduced into cells and guide the RNA-induced silencing complex (RISC) to cleave the targeted mRNA.
MicroRNA (miRNA): Endogenously produced, miRNAs are also small RNA molecules (around 22 nucleotides) that play a role in post-transcriptional regulation. They bind to target mRNAs and inhibit translation or induce mRNA degradation. MiRNAs are involved in various cellular processes, including development and differentiation.
siRNA Mechanism: SiRNAs are introduced into cells, incorporated into the RISC, and guide the RISC to complementary mRNA sequences. The RISC then cleaves the target mRNA, preventing its translation.
miRNA Mechanism: MiRNAs are transcribed from DNA, processed, and incorporated into the RISC. They bind to target mRNAs, leading to translational repression or mRNA degradation.