Editing Mutation (section)

==== Large-scale mutations ====
{{See also|Chromosome abnormality}}

Large-scale mutations in [[chromosome|chromosomal]] structure include:
* Amplifications (or [[gene duplication]]s) or repetition of a chromosomal segment or presence of extra piece of a chromosome broken piece of a chromosome may become attached to a homologous or non-homologous chromosome so that some of the genes are present in more than two doses leading to multiple copies of all chromosomal regions, increasing the dosage of the genes located within them.
* [[Polyploidy]], duplication of entire sets of chromosomes, potentially resulting in a separate breeding population and [[speciation]].
* Deletions of large chromosomal regions, leading to loss of the genes within those regions.
* Mutations whose effect is to juxtapose previously separate pieces of DNA, potentially bringing together separate genes to form functionally distinct [[fusion gene]]s (e.g., [[Philadelphia chromosome|bcr-abl]]).
* Large scale changes to the structure of [[chromosome]]s called [[chromosomal rearrangement]] that can lead to a decrease of fitness but also to speciation in isolated, inbred populations. These include:
** [[Chromosomal translocation]]s: interchange of genetic parts from nonhomologous chromosomes.
** [[Chromosomal inversion]]s: reversing the orientation of a chromosomal segment.
** Non-homologous [[chromosomal crossover]].
** Interstitial deletions: an intra-chromosomal deletion that removes a segment of DNA from a single chromosome, thereby apposing previously distant genes. For example, cells isolated from a human [[astrocytoma]], a type of brain tumour, were found to have a chromosomal deletion removing sequences between the Fused in [[Glioblastoma]] (FIG) gene and the receptor tyrosine kinase (ROS), producing a fusion protein (FIG-ROS). The abnormal FIG-ROS fusion protein has constitutively active kinase activity that causes [[Carcinogenesis|oncogenic]] transformation (a transformation from normal cells to cancer cells).
* [[Loss of heterozygosity]]: loss of one [[allele]], either by a deletion or a genetic recombination event, in an organism that previously had two different alleles.