Practice question

Unlike siRNA and miRNA requiring Dicer RNase III and Drosha, piRNA biogenesis proceeds independently of those enzymes. Primary piRNAs derive from long single-stranded precursors transcribed from piRNA clusters, cleaved by mitochondrial endonuclease Zucchini PLD6 trimming 5' ends, followed by 3' trimming via exonuclease Nibbler and 2'-O-methylation by Hen1 stabilizing terminus. Amplification via ping-pong between PIWI proteins Aubergine and Ago3 slicing targets generates secondary piRNAs without Dicer. Hence standard RNAi enzymes dispensable, explaining answer none. This alternative biogenesis reflects dedicated germline pathway for transposon suppression rather than conventional dsRNA dicing mechanism conserved elsewhere across kingdoms significantly.