miRNAs and siRNAs have overlapping functions and mechanisms - both direct post-transcriptional silencing of target genes through RNAi pathways. However, there are a few key differences: - Origin: miRNAs are produced from endogenous genes; siRNAs come from exogenous dsRNA. - Complementarity: miRNAs have imperfect binding to targets, while siRNAs match their mRNA targets perfectly. - Range: Each miRNA regulates multiple genes; siRNAs silence individual targets.