Practice question

Retrotransposon mobility requires RNA intermediate synthesized by RNA polymerase II from internal promoter, resulting transcript serves both as mRNA for reverse transcriptase and as template for reverse transcription. Endonuclease nicks target DNA providing free 3'-OH used by reverse transcriptase to prime cDNA synthesis in target-primed reverse transcription mechanism typical of non-LTR elements, or by integrase-mediated insertion for LTR elements. New DNA copy integrates while donor remains, demonstrating mandatory RNA stage unique to Class I elements enabling replicative amplification. This principle illustrates essential molecular mechanisms governing replication fidelity and mutation fixation relevant for exam interpretation.