Detection of double- and single-stranded siRNAs. 32P-end labeled double-stranded siRNA (-) was heat denatured (+) and run on a non-denaturing polyacrylamide gel to provide mobility markers for ds and ss siRNAs (left hand side). Gel-purified Tc9si and Dc9si were heat denatured and separated on a non-denaturing gel along with the mobility markers described above. Regions of the gel marked 1–5 (left hand side) and containing Tc9si and Dc9si were excised, RNA recovered and detected by ribonuclease protection assay on denaturing gels (right hand side). Gel slice number is indicated at the top and heat treatment to the right.