Small interfering RNA — or siRNA -- is a class of 20-25 nucleotide-long double-stranded RNA molecules that play a variety of roles in biology. Jayakrishna Ambati, M.D., professor and vice chair of Ophthalmology and Visual Sciences at the University of Kentucky, College of Medicine, explores the mechanisms of siRNA-mediated RNA interferences and off-target effects. Ambati describes the unexpected in vivo effects of siRNA in angiogenesis and the impact of siRNA therapeutics through pharmacogenomic investigation. From the Series:Dean’s Distinguished Lecture Series