Structure and replication of retrotransposons. a Schematic representations of long terminal repeat (LTR) and non-LTR retrotransposons not drawn to scale. Blue boxes with white arrowheads indicate LTRs, and U3-R-U5 indicate regions of LTRs. EN- endonuclease, IN- integrase, pA- poly(A) sequence, PR- protease, RT- reverse transcriptase, RT-RH- reverse transcriptase/RNase H, UTR- untranslated region. b Graphic representation of major steps of retrotransposition through target-primed reverse transcription for non-LTR retrotransposons. c Graphic representation of major steps of retrotransposition for LTR retrotransposons. Colors of ellipses correspond to proteins from panel a, wavy lines represent RNA, boxed arrowheads represent LTRs, and thin blue arrows represent DNA strands newly synthesized by reverse transcriptase.