The present invention provides double-stranded RNA molecules that are asymmetrical in strand length. The RNA molecule of the invention, the asymmetric RNA duplex, has one or two overhangs at the end. In one aspect, these novel RNA duplex molecules serve as effective mimetics of miRNA. In another aspect, they are designed to function as effective inhibitors of miRNA. Accordingly, the RNA molecules of the present invention can be used to modulate miRNA pathway activities, with tremendous implications for research, drug discovery and development, and treatment of human diseases.
