They get arrested in the G1 phase, for example,

就比如说它们在G1期停滞不前
and they never progress through to the S phase

永远不能到达
where they synthesize DNA.

合成DNA的S期
Cells can stop in their lifetime at some point in the cell cycle

细胞生命期可以停止在细胞周期的某个点
and persist for long periods of time.

并保持很长时间
This process of cell proliferation or cell division is,

细胞增殖和分裂的过程
of course, very important during development of an embryo.

在胚胎发育中至关重要
During development of the embryo

胚胎的发育
it goes from being a single cell,

始于一个单一细胞
the fertilized egg,

即受精卵
to being a multi-cellular organism

直到形成一个以十亿计数量的细胞构成的
with billions of cells in it.

多细胞有机体[婴儿大概两千亿细胞]