Editing Germ cell (section)

==Introduction==
Multicellular [[eukaryote]]s are made of two fundamental cell types: '''germ''' and '''somatic''' cells. Germ cells produce gametes and are the only cells that can undergo [[meiosis]] as well as [[mitosis]]. [[Somatic cell]]s are all the other cells that form the building blocks of the body and they only divide by mitosis. The lineage of germ cells is called the [[germline]]. Germ cell specification begins during [[cleavage (embryo)|cleavage]] in many animals or in the [[epiblast]] during [[gastrulation]] in [[bird]]s and [[mammal]]s. After transport, involving passive movements and active migration, germ cells arrive at the developing gonads. In humans, sexual differentiation starts approximately 6 weeks after conception. The end-products of the germ cell cycle are the egg or sperm.<ref>{{cite journal | vauthors = Kunwar PS, Lehmann R | title = Developmental biology: Germ-cell attraction | journal = Nature | volume = 421 | issue = 6920 | pages = 226–227 | date = January 2003 | pmid = 12529629 | doi = 10.1038/421226a | s2cid = 29737428 | doi-access = free | bibcode = 2003Natur.421..226K }}</ref>

Under special conditions ''[[in vitro]]'' germ cells can acquire properties similar to those of [[embryonic stem cells]] (ESCs). The underlying mechanism of that change is still unknown. These changed cells are then called embryonic germ cells. Both cell types are [[pluripotent]] in vitro, but only ESCs have proven pluripotency in vivo. Recent studies have demonstrated that it is possible to give rise to primordial germ cells from ESCs.<ref>{{cite journal | vauthors = Turnpenny L, Spalluto CM, Perrett RM, O'Shea M, Hanley KP, Cameron IT, Wilson DI, Hanley NA | display-authors = 6 | title = Evaluating human embryonic germ cells: concord and conflict as pluripotent stem cells | journal = Stem Cells | volume = 24 | issue = 2 | pages = 212–220 | date = February 2006 | pmid = 16144875 | doi = 10.1634/stemcells.2005-0255 | s2cid = 20446427 | doi-access = free }}</ref>