Comparison of transposition cycles of four subclasses of transposable elements (TEs). Simplified representations of major steps in the transposition cycles of two subclasses of DNA transposons (cut-and-paste and peel-and-paste) and two subclasses of retrotransposons (long terminal repeat (LTR) and non-LTR) are shown. Light gray and lavender lines represent donor and target genomic sites, respectively. Boxed arrowheads indicate terminal inverted repeats (cut-and-paste) or LTRs. Curved black arrows indicate repair of the donor site after transposon excision, small purple or blue arrows represent new DNA synthesis, and wavy lines represent RNA. TP- transposase (DDE-type for cut-and-paste or HUH nuclease/helicase-type for peel-and-paste), RT- reverse transcriptase, IN- integrase, EN- endonuclease domain.