Table 1. TFT^R colony frequencies (×10⁵) following DSB-induction^a.

Cell line	Type of DNA electroporated
	pCMV-I-SceI	pCMV-I-SceI + φX174/HaeIII	pCMV-I-SceI + φX174 RF I	Mock
2	138	116	76	1.3
4	51	60	58	1.9

^aCells were electroporated with either pCMV-I-SceI alone, pCMV-I-SceI plus a HaeIII digest of φX174 DNA, pCMV-I-SceI plus supercoiled φX174 RF I DNA, or PBS alone (mock) and then selected in TFT as described in Materials and Methods. The number of TFT^R colonies recovered was divided by the number of cells plated following electroporation; this quotient was multiplied by 10⁵ and is presented in the table.