As an example, DNA synthesis, i.e. 3HT incorporation into nucleic acids in B1B cells is shown (green triangles). At time 0, 3HT incorporation starts; at 1 hour, 500 μM MMS is added. In this case, the DNA synthesis rate increases. Onset of apoptosis would lead to fast degeneration of the DNA (red dotted line). At 2 hours, HU is added. In case of replication as the origin of the DNA synthesis, the incorporation would stop (blue dotted line). Instead, incorporation continues nearly unaffected, indicating that now all of DNA synthesis is managed through the repair system. Thus, B1B cells are blind to DNA damage and repair DNA instead of initiating apoptosis. After the experiment, microscopic analysis showed no sign of cellular damage. Two independent experiments with two independent samples per value are carried out.
