Final answer:
MicroRNAs (miRNAs) inhibit gene expression in eukaryotic cells by degrading or inhibiting the translation of target mRNAs. They are processed from pre-miRNAs by Drosha and Dicer enzymes and function through the RISC complex. Abnormal expression of miRNAs is associated with diseases, including cancer, making them targets for therapeutic intervention.
Step-by-step explanation:
MicroRNAs (miRNAs) are short, non-coding RNA molecules that regulate gene expression post-transcriptionally. They are synthesized as pre-miRNA in the nucleus and processed into mature miRNAs by Drosha and Dicer endonucleases. Mature miRNAs bind to RISC (RNA-induced silencing complex), leading to the degradation or inhibition of target mRNA, which effectively silences the gene. Therefore, miRNAs act as inhibitors of gene expression by decreasing mRNA levels and preventing translation.
Moreover, miRNAs play a significant role in various diseases, including cancer, where certain miRNAs are upregulated. Understanding and controlling miRNA function has therapeutic potential, as siRNAs and miRNAs are being investigated as tools to modulate gene expression in disease treatment.