Practice question

Canonical stem cell properties include prolonged self-renewal through cell cycle regulators such as telomerase, Bmi1 Polycomb protein, and p27 control, capacity to differentiate into multiple mature types under niche instructions, and dependence on niche signals for maintenance of undifferentiated state. Transit-amplifying and terminal differentiation pathways ensure progeny exit cell cycle and perform specialized functions such as absorption or contraction. If a cell terminally differentiated upon each division, it would lose self-renewal and rapidly exhaust the pool, contradicting lifelong regeneration observed in intestine, skin, and blood where stem cells persist for decades continuously producing progeny.