Dot plot analysis for the expression of the CD117/Sca-1, CD117/CD34, and CD71/TER119 antigens in marrow cells from 16- to 20-month-old F1-F2 normal littermates with predominant C57BL/6, DBA/2, or CD1 backgrounds, as indicated. The gates defining stem and progenitor cells as well as those corresponding to maturing erythroblasts are CD117^pos/Sca-1^pos, CD117^pos/CD34^{dim to high}, and CD71^pos/Ter119^pos, respectively, as indicated. The number in each quadrant indicates the frequency of marrow cells in that gate. Similar results were obtained in at least 3 mice for each strain, and mean (± SD) of results obtained in different mice is presented in Table 4.