Editing Cell cycle (section)

====S phase (DNA replication)====
{{main|S phase}}
The ensuing [[S phase]] starts when [[DNA synthesis]] commences; when it is complete, all of the [[chromosome]]s have been replicated, i.e., each chromosome consists of two sister [[chromatid]]s. Thus, during this phase, the amount of DNA in the cell has doubled, though the [[ploidy]] and number of chromosomes are unchanged. Rates of RNA [[Transcription (genetics)|transcription]] and [[Protein biosynthesis|protein synthesis]] are very low during this phase. An exception to this is [[histone]] production, most of which occurs during the S phase.<ref name="pmid7199388">{{cite journal | vauthors = Wu RS, Bonner WM | title = Separation of basal histone synthesis from S-phase histone synthesis in dividing cells | journal = Cell | volume = 27 | issue = 2 Pt 1 | pages = 321–330 | date = December 1981 | pmid = 7199388 | doi = 10.1016/0092-8674(81)90415-3 | s2cid = 12215040 }}</ref><ref name="pmid12370293">{{cite journal | vauthors = Nelson DM, Ye X, Hall C, Santos H, Ma T, Kao GD, Yen TJ, Harper JW, Adams PD | display-authors = 6 | title = Coupling of DNA synthesis and histone synthesis in S phase independent of cyclin/cdk2 activity | journal = Molecular and Cellular Biology | volume = 22 | issue = 21 | pages = 7459–7472 | date = November 2002 | pmid = 12370293 | pmc = 135676 | doi = 10.1128/MCB.22.21.7459-7472.2002 }}</ref><ref name="pmid14018040">{{cite journal | vauthors = Cameron IL, Greulich RC | title = Evidence for an essentially constant duration of DNA synthesis in renewing epithelia of the adult mouse | journal = The Journal of Cell Biology | volume = 18 | issue = 1 | pages = 31–40 | date = July 1963 | pmid = 14018040 | pmc = 2106275 | doi = 10.1083/jcb.18.1.31 }}</ref>