Editing Stem cell (section)

===Self-renewal===
Two mechanisms ensure that a stem cell population is maintained (does not shrink in size):

1. [[Asymmetric cell division]]: a stem cell divides into one mother cell, which is identical to the original stem cell, and another daughter cell, which is differentiated.

When a stem cell self-renews, it divides and disrupts the undifferentiated state. This self-renewal demands control of cell cycle as well as upkeep of multipotency or pluripotency, which all depends on the stem cell.<ref>Shenghui, H. E., Nakada, D., & Morrison, S. J. (2009). Mechanisms of stem cell self-renewal. Annual Review of Cell and Developmental, 25, 377–406.</ref>

H.

Stem cells use [[telomerase]], a protein that restores [[telomeres]], to protect their DNA and extend their cell division limit (the [[Hayflick limit]]).<ref>{{cite journal | vauthors = Cong YS, Wright WE, Shay JW | title = Human telomerase and its regulation | journal = Microbiology and Molecular Biology Reviews | volume = 66 | issue = 3 | pages = 407–425, table of contents | date = September 2002 | pmid = 12208997 | pmc = 120798 | doi = 10.1128/MMBR.66.3.407-425.2002 | doi-access = free }}</ref>