File:LTR retrotransposon.png

English: A. Genetic structure of LTR-retrotransposons (gypsy-type). B. Mechanism of retrotransposition, occurring inside viral-like particles in the cytoplasm. Reverse-transcription initiates at a host tRNA primer binding site (PBS) located immediately downstream of the 5’LTR. The newly synthesized minus-strand cDNA copy of the 5’LTR is then transferred to the 3’LTR and used as a primer for reverse-transcription of the entire minus-strand sequence. An RNase H-resistant polypurine tract then serves as a primer for plus-strand synthesis of the 3’LTR and complementary PBS. The newly-synthesized plus-strand PBS then associates with the already-synthesized minus-strand PBS, and double-stranded cDNA is finally produced. Double-stranded cDNA is then transferred to the nucleus by integrase proteins, and a new copy is integrated into the genome.