TABLE 2.

Effect of irradiation on signal joint formation in wild-type and SCID thymic lymphomas^a

Cell line	Irradiation	%R	IR/C	% Fidelity (n)
VL3-3M2	−	1.87		76 (30)
	+	3.56	1.90	85 (20)
LK6.2	−	14.51		35 (34)
	+	12.23	0.84	23 (34)
LK3C	−	4.01		47 (15)
	+	1.51	0.38	33 (15)

^aExperiments to measure the efficiency and fidelity of signal joint formation were performed as described in Table 1, except that cell lines were transfected with the deletional signal joint substrate pWTSJΔ 30 min before irradiation. To assess the fidelity of signal joint formation, recombinant plasmids were purified from chloramphenicol-resistant colonies and digested with ApaLI. Shown are the percentages of colonies that could be digested with ApaLI (%R), indicating that they had precise signal joints. The number (n) of colonies tested in each group is shown. IR/C, ratio of recombination frequencies of irradiated cultures to those of control cultures.