One abundant human retrotransposon, the L1 element (sometimes referred to as LINE-1, a long interspersed nuclear element), is transcribed into RNA by a host cell’s RNA polymerase.
B.
A double-stranded DNA copy of this RNA is then made using an enzyme called reverse transcriptase, an unusual DNA polymerase that can use RNA as a template.
C.
The reverse transcriptase is encoded by the L1 element itself.
D.
The DNA copy of the element is then free to reintegrate into another site in the genome.