The DNA damage checkpoint promotes HR and suppresses break-induced LOH. (A) Percentage DSB-induced marker loss of Ch16-RMGAH in wild-type (TH2130), rad26Δ (TH3410), crb2Δ (TH3383) and OPcdc25 (TH3395) backgrounds. (B) The DNA replication checkpoint does not suppress break-induced LOH. Percentage DSB-induced marker loss of Ch16-RMGAH in wild-type (TH2130), mrc1Δ (TH3253) and cds1Δ (TH3256) backgrounds. (C) An additional role for Chk1 activation in promoting HR and suppressing break-induced LOH. Percentage DSB-induced marker loss of Ch16-YAMGH in wild-type (TH3317), chk1Δ (TH3153), rad9-T412A (TH5381), rad4.110 (TH4481) and rad3Δchk1Δ (TH3623) backgrounds. For (A), (B) and (C) the levels of NHEJ/SCC, GC, Ch16 loss and extensive LOH are shown. Data are the mean of three experiments and standard errors of the mean are indicated. The asterisk (*) represents P < 0.05 compared to wild-type.