Editing Gene duplication (section)

===Aneuploidy===
[[Aneuploidy]] occurs when nondisjunction at a single chromosome results in an abnormal number of chromosomes. Aneuploidy is often harmful and in mammals regularly leads to spontaneous abortions (miscarriages).  Some aneuploid individuals are viable, for example trisomy 21 in humans, which leads to [[Down syndrome]].  Aneuploidy often alters gene dosage in ways that are detrimental to the organism; therefore, it is unlikely to spread through populations.