TET processivity can be viewed at three levels, the physical, chemical and genetic levels.  Physical processivity refers to the ability of a TET protein to slide along the DNA from one CpG site to another.  An in vitro study showed that DNA-bound TET does not preferentially oxidize other CpG sites on the same DNA molecule, indicating that TET is not physically processive.  Chemical processivity refers to the ability of TET to catalyze the oxidation of 5mC iteratively to 5caC without releasing its substrate.  It appears that TET can work through both chemically processive and non‑processive mechanisms depending on reaction conditions.  Genetic processivity refers to the genetic outcome of TET‑mediated oxidation in the genome, as shown by mapping of the oxidized bases.  In mouse embryonic stem cells, many genomic regions or CpG sites are modified so that 5mC is changed to 5hmC but not to 5fC or 5caC, whereas at many otherCpG sites 5mCs are modified to 5fC or 5caC but not 5hmC, suggesting that 5mC is processed to different states at different genomic regions or CpG sites.