Practice question

MicroRNA biogenesis starts in nucleus where pri-miRNAs transcribed by Pol II are cropped by Microprocessor complex containing Drosha RNase III and DGCR8 cofactor. Drosha measures about eleven base pairs from basal junction cleaving hairpin releasing ~70 nucleotide pre-miRNA with two-nucleotide 3' overhang. Pre-miRNA exported via Exportin-5 Ran-GTP pathway to cytoplasm for Dicer processing to mature duplex. Nuclear localization separates processing from translation enabling quality control coupled to splicing. Some mirtrons bypass Drosha via splicing. Compartmentalized maturation ensures ordered steps, prevents premature RISC loading, and integrates miRNA production with transcriptional regulation and cellular signaling pathways efficiently.