Figure 4A summarizes the results of direct testing for negative genetic interactions between the cancer-gene orthologs mre11Δ, bub1Δ, and sgs1Δ and mutant alleles of CDC45, MCM10, primase, MCM, or GINS complexes. In almost every case, interactions are observed between each cancer−gene ortholog and at least one member of the Ctf4-interacting complexes. Because all of the Ctf4-interacting genes are essential, partial loss-of-function (i.e., DAmP or ts) alleles are used, potentially explaining why not all genes tested show interactions. Here, MCM10 is linked to cancer.