Practice question

Progenitor cells, often termed transit-amplifying or intermediate progenitors, derive from rare stem divisions and exhibit rapid proliferation but limited self-renewal, undergoing finite mitoses before obligatory terminal differentiation and cell cycle exit. They express lineage-specific transcription factors committing them to particular path such as myeloid progenitors expressing PU.1 and C/EBPalpha or basal keratinocyte progenitors expressing Krt5 but not sustaining lifelong pool. Unlike genuine stem cells they lack indefinite telomerase, cannot long-term reconstitute ablated tissue upon serial transplantation, and are not totipotent, serving mainly as amplification stage increasing output without endangering stem genome integrity.