Editing Cell (biology) (section)

=== Replication ===

{{main|Cell division}}

Cell division involves a single cell (called a ''mother cell'') dividing into two daughter cells. This leads to growth in [[multicellular organism]]s (the growth of [[biological tissue|tissue]]) and to procreation ([[vegetative reproduction]]) in [[unicellular organism]]s. [[Prokaryote|Prokaryotic]] cells divide by [[binary fission]], while [[Eukaryote|eukaryotic]] cells usually undergo a process of nuclear division, called [[mitosis]], followed by division of the cell, called [[cytokinesis]]. A [[diploid]] cell may also undergo [[meiosis]] to produce haploid cells, usually four. [[Haploid]] cells serve as [[gamete]]s in multicellular organisms, fusing to form new diploid cells.

[[DNA replication]], or the process of duplicating a cell's genome,<ref name="NCBI"/> always happens when a cell divides through mitosis or binary fission. This occurs during the S phase of the [[cell cycle]].

In meiosis, the DNA is replicated only once, while the cell divides twice. DNA replication only occurs before [[meiosis I]]. DNA replication does not occur when the cells divide the second time, in [[meiosis II]].<ref>{{cite book|title=Campbell Biology{{snd}}Concepts and Connections|year=2009|publisher=Pearson Education|page=138}}</ref> Replication, like all cellular activities, requires specialized proteins for carrying out the job.<ref name="NCBI"/>