Editing Robertsonian translocation (section)

{{Short description|Human chromosomal abnormality}}
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[[File:Robertsonian translocation.png|thumb|A Robertsonian translocation. The short arms of the chromosomes (shown on right) are often lost ]]

'''Robertsonian translocation''' ('''ROB''') is a [[Chromosome abnormality|chromosomal abnormality]] where the entire long arms of two different [[chromosome|chromosomes]] become fused to each other. It is the most common form of [[chromosomal translocation]] in humans, affecting 1 out of every 1,000 babies born.<ref>E. Therman, B. Susman and C. Denniston. The nonrandom participation of human acrocentric chromosomes in Robertsonian translocations. ''Annals of Human Genetics'' 1989;53:49-65.</ref> It does not usually cause medical problems, though some people may produce [[Gamete|gametes]] with an incorrect number of chromosomes, resulting in a risk of miscarriage. In rare cases this [[Chromosomal translocation|translocation]] results in [[Down syndrome]] and [[Patau syndrome]].<ref name=":1">{{Cite web |url=https://www.rarechromo.org/media/information/Other/Robertsonian%20Translocations%20FTNW.pdf |title=Unique: Rare Chromosome Disorder Support Group |access-date=2019-02-17 |archive-date=2019-02-18 |archive-url=https://web.archive.org/web/20190218082031/https://www.rarechromo.org/media/information/Other/Robertsonian%20Translocations%20FTNW.pdf |url-status=dead }}</ref> Robertsonian translocations result in a reduction in the number of chromosomes. A Robertsonian evolutionary fusion, which may have occurred in the common ancestor of humans and other [[great ape]]s, is the reason humans have 46 chromosomes while all other primates have 48. Detailed DNA studies of [[chimpanzee]], [[orangutan]], [[gorilla]] and [[bonobo]] [[ape]]s has determined that where [[human]] [[chromosome 2]] is present in our DNA in all four great apes this is split into two separate chromosomes typically numbered 2a and 2b.<ref name="pmid28333343">{{cite journal |last1=Chiatante |first1=Giorgia |last2=Giannuzzi |first2=Giuliana |last3=Calabrese |first3=Francesco Maria |last4=Eichler |first4=Evan E. |last5=Ventura |first5=Mario |title=Centromere Destiny in Dicentric Chromosomes: New Insights from the Evolution of Human Chromosome 2 Ancestral Centromeric Region |journal=[[Molecular Biology and Evolution]] |date=1 July 2017 |volume=34 |issue=7 |pages=1669–1681 |doi=10.1093/molbev/msx108 |pmid=28333343 |pmc=5722054}}</ref><ref name="pmid25984837">{{cite journal |last1=Pratas |first1=Diogo |last2=Silva |first2=Raquel M. |last3=Pinho |first3=Armando J. |last4=Ferreira |first4=Paulo J.S.G. |title=An alignment-free method to find and visualise rearrangements between pairs of DNA sequences |journal=[[Scientific Reports]] |date=18 May 2015 |volume=5 |issue=1 |pages=1203 |doi=10.1038/srep10203 |pmid=25984837 |pmc=4434998|bibcode=2015NatSR...510203P }}</ref> Similarly, the fact that horses have 64 chromosomes and donkeys 62, and that they can still have common, albeit usually infertile, offspring,<ref>More details under [[Mule]] and [[Hinny]].</ref> may be due to a Robertsonian evolutionary fusion at some point in the descent of today's donkeys from their common ancestor.<ref name="equus" />