Editing Mitosis (section)

===Errors and other variations===
[[File:Atypical mitosis.jpg|thumb|right|200px|An abnormal (tripolar) mitosis (12 o'clock position) in a precancerous lesion of the stomach ([[H&E stain]])]]
Errors can occur during mitosis, especially during early [[embryo]]nic development in humans.<ref>{{cite journal | vauthors = Mantikou E, Wong KM, Repping S, Mastenbroek S | title = Molecular origin of mitotic aneuploidies in preimplantation embryos | journal = Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease | volume = 1822 | issue = 12 | pages = 1921–30 | date = December 2012 | pmid = 22771499 | doi = 10.1016/j.bbadis.2012.06.013 | doi-access = free }}</ref> During each step of mitosis, there are normally checkpoints as well that control the normal outcome of mitosis.<ref>{{cite journal |last1=Wassmann |first1=Katja |last2=Benezra |first2=Robert |title=Mitotic checkpoints: from yeast to cancer |journal=Current Opinion in Genetics & Development |date=February 2001 |volume=11 |issue=1 |pages=83–90 |doi=10.1016/S0959-437X(00)00161-1 |pmid=11163156 }}</ref> But, occasionally to almost rarely, mistakes will happen. Mitotic errors can create [[aneuploidy|aneuploid]] cells that have too few or too many of one or more chromosomes, a condition associated with [[cancer]].<ref name="Draviam-2004"/><ref>{{cite journal | vauthors = Santaguida S, Amon A | title = Short- and long-term effects of chromosome mis-segregation and aneuploidy | journal = Nature Reviews. Molecular Cell Biology | volume = 16 | issue = 8 | pages = 473–85 | date = August 2015 | pmid = 26204159 | doi = 10.1038/nrm4025 | hdl = 1721.1/117201 | hdl-access = free }}</ref>  Early human embryos, cancer cells, infected or intoxicated cells can also suffer from pathological division into three or more daughter cells (tripolar or multipolar mitosis), resulting in severe errors in their chromosomal complements.<ref name="Kalatova-2015"/>

In ''[[nondisjunction]]'', sister chromatids fail to separate during anaphase.<ref name="Iourov-2006">{{cite book | vauthors = Iourov IY, Vorsanova SG, Yurov YB | veditors = Jeon KJ |title=International Review Of Cytology: A Survey of Cell Biology|date=2006|publisher=Academic Press|location=Waltham, MA |isbn=9780080463506|page=146|chapter=Chromosomal Variations in Mammalian Neuronal Cells: Known Facts and Attractive Hypotheses |volume=249}}</ref> One daughter cell receives both sister chromatids from the nondisjoining chromosome and the other cell receives none. As a result, the former cell gets three copies of the chromosome, a condition known as ''[[trisomy]]'', and the latter will have only one copy, a condition known as ''[[monosomy]]''. On occasion, when cells experience nondisjunction, they fail to complete cytokinesis and retain both nuclei in one cell, resulting in [[binucleated cells]].<ref>{{cite journal | vauthors = Shi Q, King RW | title = Chromosome nondisjunction yields tetraploid rather than aneuploid cells in human cell lines | journal = Nature | volume = 437 | issue = 7061 | pages = 1038–42 | date = October 2005 | pmid = 16222248 | doi = 10.1038/nature03958 | bibcode = 2005Natur.437.1038S }}</ref>

''[[Anaphase lag]]'' occurs when the movement of one chromatid is impeded during anaphase.<ref name="Iourov-2006"/> This may be caused by a failure of the mitotic spindle to properly attach to the chromosome. The lagging chromatid is excluded from both nuclei and is lost. Therefore, one of the daughter cells will be monosomic for that chromosome.

''[[Endoreduplication]]'' (or endoreplication) occurs when chromosomes duplicate but the cell does not subsequently divide. This results in [[polyploid]] cells or, if the chromosomes duplicates repeatedly, [[polytene chromosomes]].<ref name="Iourov-2006"/><ref name="Edgar-2001">{{cite journal | vauthors = Edgar BA, Orr-Weaver TL | title = Endoreplication cell cycles: more for less | journal = Cell | volume = 105 | issue = 3 | pages = 297–306 | date = May 2001 | pmid = 11348589 | doi = 10.1016/S0092-8674(01)00334-8 | doi-access = free }}</ref> Endoreduplication is found in many species and appears to be a normal part of [[developmental biology|development]].<ref name="Edgar-2001"/> [[Endomitosis]] is a variant of endoreduplication in which cells replicate their chromosomes during S phase and enter, but prematurely terminate, mitosis. Instead of being divided into two new daughter nuclei, the replicated chromosomes are retained within the original nucleus.<ref name="Lilly-2005"/><ref name="Lee-2009">{{cite journal | vauthors = Lee HO, Davidson JM, Duronio RJ | title = Endoreplication: polyploidy with purpose | journal = Genes & Development | volume = 23 | issue = 21 | pages = 2461–77 | date = November 2009 | pmid = 19884253 | pmc = 2779750 | doi = 10.1101/gad.1829209 }}</ref> The cells then re-enter G<sub>1</sub> and S phase and replicate their chromosomes again.<ref name="Lee-2009"/> This may occur multiple times, increasing the chromosome number with each round of replication and endomitosis. [[Platelet]]-producing [[megakaryocytes]] go through endomitosis during cell differentiation.<ref name="Italiano-2003"/><ref>{{cite journal | vauthors = Vitrat N, Cohen-Solal K, Pique C, Le Couedic JP, Norol F, Larsen AK, Katz A, Vainchenker W, Debili N | title = Endomitosis of human megakaryocytes are due to abortive mitosis | journal = Blood | volume = 91 | issue = 10 | pages = 3711–23 | date = May 1998 | pmid = 9573008 | doi = 10.1182/blood.V91.10.3711 | doi-access = free }}</ref>

''[[Amitosis]]'' in ciliates and in animal placental tissues results in a random distribution of parental alleles.

''Karyokinesis without cytokinesis'' originates [[multinucleated]] cells  called [[coenocytes]].