Table 1.

Mitochondrial DNA molecule types observed in the transmission electron microscopic (TEM) analysis of parental HEK293T and MGME1 knockout (KO) cells, without or with 72 h ddC treatment.

	HEK untreated	HEK ddC	MGME1 KO untreated	MGME1 KO ddC
N	400	400	400	100
Catenated or recombining	9%	15%	11%	29%
Dimeric circles	0.1%	0.2%	1.3%	ND
Replicating	5%	8%	5%	19%
of which broken	10%	40%	57%	32%

N = number of counted molecules. Note that catenated and recombining circles cannot be distinguished from the TEM imagery. Only 100 molecules were counted from the ddC treated MGME1 KO due to high levels of linear mtDNA in these samples and therefore rare dimeric molecules were not detected (ND).