The initial uridine of primary piRNAs does not create the tenth adenine that Is the hallmark of secondary piRNAs.
Wang W, Yoshikawa M, Han BW, Izumi N, Tomari Y, Weng Z, Zamore PD. The initial uridine of primary piRNAs does not create the tenth adenine that Is the hallmark of secondary piRNAs. Mol Cell. 2014 Dec 04; 56(5):708-16.