BRCA1 and cancer: The SNVs induced in mock-treated WT cells could be expected to correlate with the aging-specific signature 1, which is dominated by CG>TG mutations at methylated CpGs.11 The correlation observed here is fairly weak, as CG>TG changes are overrepresented in human cancer samples to a far greater extent than in the experimental DT40 samples, where the WT, BRCA1+/− and BRCA2+/− samples all showed 11-fold overrepresentation (Figure 5d).