Simulations of gene therapy in which two marked cells were included among the 300 hematopoietic stem cells (A). In the comparable simulations of (B) and (C), however, the label is not neutral. In (B), it confers a twofold self-renewal advantage to HSC, ie, the p(HSC replication) for marked cells is two times that of unmarked cells.

In the simulations of (C), a marked clone has a one-half chance of exhaustion when compared with unmarked clones, ie, the p(exhaustion of a differentiating clone) is one-half that of unmarked clones.