Figure 6 .

The average number of spontaneous SCEs per metaphase spread (MPS). (A) Spontaneous SCEs in control (AB2.2) and trex2^null cells. Trex2 deletion reduced SCEs in control AB2.2 cells (Yates-corrected chi-square test, P < 0.0001). (B) Spontaneous SCEs in control (AB2.2), blm^−/−, and trex2^null blm^−/− cells. Trex2 deletion did not reduce SCEs in blm^−/− cells (P = 0.11). Total numbers: AB2.2, 374 SCEs from 1965 chromosomes (61 metaphase spreads); trex2^null, 354 SCEs from 4020 chromosomes (106 metaphase spreads); blm^−/−, 1348 SCEs from 1900 chromosomes (50 metaphase spreads); and trex2^null blm^−/−, 1348 SCEs from 1894 chromosomes (50 metaphase spreads).