Practice question

Asymmetric division intrinsically or extrinsically partitions fate determinants, producing one daughter retaining stem cell identity within the protective niche and another exiting to differentiate. Spindle orientation, evolutionarily conserved Par polarity proteins, Numb segregation, and polarized Notch signaling ensure unequal inheritance of transcription factors and organelles. This elegant mechanism preserves constant stem pool size during steady-state homeostasis while continuously supplying progenitors for tissue turnover. In contrast, symmetric self-renewing divisions expand pool during development, while symmetric differentiation depletes it, illustrating dynamic regulation of tissue balance throughout life.