Histograms of the DNA content of (A) bone marrow megakaryocytes from 6 normal (Wild Type, top) and 8 ▵neo▵HS (Mutant, bottom) weanling mice (age 4 weeks), and (B) megakaryocytes cultured ex vivo from E12.5 fetal livers of 3 normal (Wild Type, top) and 3 ▵neo▵HS (Mutant, bottom) embryos. The mean percentage (± 1 SD) of RAMPS-positive cells in each ploidy class