As shown in Fig. 3a, the variant calls of SMAD4 (row 13) and TP53 (row 5) show the frequency pattern generated by a deletion of one allele in cancer cells: in the first case, the loss of the variant allele will decrease to zero the frequency; in the second case, the 100% frequency indicates the loss of the wild-type allele. Here, SMAD4 is linked to cancer.