After CreERT2 activation by intraperitoneal injections of 4-OHT, the loxP-flanked exon 14 in one allele of the Apc tumor suppressor is deleted all along the crypt–villus axis leading to the initial stage of the multi-step transformation process [19, 20] in either the WT or Ubc9+/− genetic background. The gene discussed is UBE2I; the disease is neoplasm.