FIGURE 1.

Replicative potential, replicative rate, and telomere shortening across the hematopoietic hierarchy. Larger cells denote more replicative capacity; darker cells denote faster replication. Cells atop the hierarchy replicate at a slow pace but have a high replicative capacity. Cells at the bottom replicate at a fast pace but have a lower replicative capacity. The length of telomeres (shown as the red caps at the end of the chromosomes) is progressively shorter toward the bottom due to the greater number of cell replications that occur moving down the hierarchy.