TABLE 1.

Cell cycle arrest and chromosomal aberrations after cross-linking of wild-type and Ercc1-Xpf mutant cells

Cell type	Treatment	No. of metaphases examined	% in first divisiona	% of metaphases with chromatid aberrationsb	% of metaphases with fusionsc	% of metaphases with chromosome aberrationsd
Wild-type ES	None	59	0	0	0	0
	3 μM MMC	57	0	2	0	1
Ercc1−/− ES	None	64	0	20	0	12
	300 nM MMC	114	46	60e	46e	50e
Wild-type CHO	None	50	6	0	0	0
	10 μM cisplatin	47	13	2	13	13
Ercc1 mutant CHO	None	50	10	0	0	2
	1 μM cisplatin	48	100	0	83	62
Xpf mutant CHO	None	50	9	4	0	0
	1 μM cisplatin	47	100	0	92	49

^aThe remainder of the cells had completed a second division in the period following exposure to MMC.

^bAberrations restricted to a single chromatid, including gaps, breaks, and radial structures.

^cAberrations involving joining of two sister chromatids within a chromosome (ring structure) or different chromosomes (tri- or quadriradials).

^dAberrations involving both sister chromatids, including gaps and breaks.

^eForty-six percent of these occurred in cells arrested in the first division.