In colorectal cancer, focusing on fidelity to human colorectal cancer aneuploidy events, our results highlighted the critical importance of synteny in transgenic studies, as not only was loss of mouse chromosome 18 (containing the tumor suppressor gene Smad4) a significant aneuploidy event (18%), additional tumors harbored focal Smad4 copy loss, potentially due to the mouse-specific proximity of Apc (mouse and human chromosomes 18 and 5, respectively). This evidence concerns the gene APC and colorectal cancer.