Changes in progenitor and stem cell numbers in BXD mice during aging. CAFC day-7, 21, and 35 were measured in young (2 months) and old (20 months) BXD mice, and the percentage increase or decrease in cell numbers during aging was calculated. (A, B, and C) Show relative changes in the numbers of CAFC day-7, day-21, and day-35, respectively. Note that the Y-axis for all three panels is the same. Three young BXD mice were used for all datapoints. The number of old BXD mice per datapoint was 1 (seven strains), 2 (five strains), or 3 (eight strains). The most extreme deviations from young CAFC day-21 and 35 numbers were seen in strains from which three animals were used (BXD-6, -15, and 29).