The effects of 5-FU on leukocytes and red blood cells were similar in each of the Mpl-tyrosine mutant mice to C57BL/6 controls; in MplTM/TM, MplIC36/IC36 and Mpl−/− mice an extended and more severe anaemia was evident prior to recovery, as was an extended period of leukopenia (Fig. 5B, C). The gene discussed is MPL; the disease is anemia.