The reduction in the numbers of hematopoietic progenitors in the fetal livers of jmj^trap/trap embryos. The numbers per fetal liver of BFU-E (A) and CFU-E colonies (B) in 11.5 dpc to 14.5 dpc embryos and CFU-GM colonies (C) in 12.5 dpc and 14.5 dpc embryos were determined. The open and closed columns indicate the average numbers of colonies from jmj^+/+ andjmj^+/trap embryos and fromjmj^trap/trap embryos, respectively. The numbers of fetal livers analyzed are shown above the columns and the error bars indicate SEM.