B6 and B6.SJL strains possess equivalent patterns of cell cycling, apoptosis, and CAFCs. (A) There were no significant differences between B6 and B6.SJL cells in any phase of the cell cycle or apoptosis in any bone marrow population tested. Values represent the mean ± SD calculated from 3 independent experiments each using 2 mice per strain. Statistical comparisons were made using the unpaired Student t test assuming unequal variance. (B) There were no significant differences in in vitro defined bone marrow HSC number (CAFCd28 and CAFCd35) between B6 and B6.SJL mice (*P < .05). Data were combined from 3 independent CAFC assays each using marrow pooled from 2 to 3 mice per strain.