To explore how existing mutational processes contribute to increased mutation burden in BCR::ABL1-positive cells, we assigned mutational signatures to individual branches of phylogenies (Fig. 3b and Extended Data Figs. 3 and 4), grouping by (1) BCR::ABL1-negative (wild-type) branches, (2) shared branch of the BCR::ABL1 clade representing the pre-CML lineage, (3) early shared branches of the BCR::ABL1 clade, representing historical early CML clonal expansion, (4) all branches of the BCR::ABL1 clade, including recent mutations and (5) early-in-life branches. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.