Flow cytometry of bone marrow cells from an animal that died of BCR/ABL disease demonstrates an increased number of megakaryocytic cells. The number of megakaryocytes staining positive for CD41 in hCD34tTA × BCR/ABL (+/+) was significantly increased compared with bone marrow cells from control animals. The top panel demonstrates surface expression of CD41 in the horizontal axis. The graph below demonstrates the difference between 10 double-transgenic induced mice versus bone marrow cells from 11 control animals, including 2 nontransgenic littermates with the same genetic background (FVB), 1 hCD34tTA single transgenic, and 8 BCR/ABL single transgenic mice. No difference was found between single transgenic and the nontransgenic wild-type controls. Percentages in top panels indicate percent positive for CD41.