Small RNA ligated to 3’ adapter and the PCR amplified library. (A) The 3’ ligation reaction was separated on a 10% urea PAGE gel showing the adapters, small RNAs and 3’ ligation products. NEB RNA ladders are shown in the left lane. (B) Small RNA library after PCR amplification was separated on a 2% agarose gel. The library and adapter dimers are indicated by arrows. The 50 bp and 1 kb DNA ladders are shown on the left and middle lanes, respectively.