Practice question

Retrotransposons lack transposase sufficient for cut-and-paste but encode reverse transcriptase capable of synthesizing DNA from RNA template, essential for copy-and-paste replicative expansion. LTR retrotransposons encode Pol protein containing reverse transcriptase, RNase H, and integrase domains homologous to retroviruses, while non-LTR LINEs encode ORF2p with apurinic endonuclease and reverse transcriptase activities mediating target-primed reverse transcription. Without reverse transcriptase, RNA intermediate could not be converted to integratable cDNA, rendering retrotransposition impossible, hence its conservation in autonomous retroelements. This principle illustrates essential molecular mechanisms governing replication fidelity and mutation fixation relevant for exam interpretation.