Before revision:  We previously speculated that the mechanism of DNA to DNA transcription might be similar to that of DNA to RNA transcription, but there is another mechanism that we think is most likely to be true. The mechanism is called endonuclease dependent transcript cutout  , in which a copy of ssDNA fragment (transcript) between two nicks produced by nicking endonuclease is released from double-stranded DNA region in the genome by an unknown ssDNA fragment-releasing enzyme.
After revision:  We previously speculated that the mechanism of DNA to DNA transcription might be similar to that of DNA to RNA transcription, but now we propose that endonuclease dependent transcript cutout , in which a copy of ssDNA fragment (transcript) between two nicks produced by nicking endonuclease is released from double-stranded DNA region in the genome by an unknown ssDNA fragment-releasing enzyme.