Abstract

The piRNA class of small RNAs are distinct from other small RNAs by their ∼26–31 nucleotide size, single‐strandedness and strand‐specificity as well as by the clustered arrangement of their origins. Here, we highlight how these features are reminiscent of the mechanisms of DNA replication, and then present three models suggesting that the origin of piRNAs may be mechanistically similar to key processes in DNA replication. BioEssays 29:382–385, 2007. © 2007 Wiley Periodicals, Inc.