DGR homing occurs via a unique, “copy and replace” pathway that substitutes parental VR sequences with diversified cDNA copies of TR transcripts. cDNA integration at the 3′ end of VR is proposed to occur via a TPRT mechanism, while integration at the 5′ end of VR requires short stretches of TR/VR sequence homology and occurs through template-switching and/or strand displacement. Adenine mutagenesis most likely occurs during minus-strand cDNA synthesis by the DGR-encoded RT. The resulting mismatches in VR DNA strands could be resolved via DNA replication. Pink arrows and bars, cDNAs and cDNA-derived sequences. “N”, any of the four deoxyribonucleotides. Dashed lines, TR flanking sequences. See the text for details.