BRCA1 and cancer: The comparison of triplet SNV spectra with triplet mutation signatures derived from cancer genomes26,27 using t-SNE showed closest correlation of the WT DT40 spontaneous spectrum with the ageing-associated signature 1, whereas SNV mutagenesis in the DT40 BRCA1−/− cells was best correlated with signature 3 typical of BRCA1/2 mutant cancers (Fig. 2g) as published earlier.16,17 The calculation of Pearson correlations or hierarchical clustering supports these findings (Supplementary Fig. S5).