三核苷酸重複序列擴張疾病(Trinucleotide Repeat Disorders)
若基因突變的方式是以三個核甘酸為單位，重複擴張至不正常的數量，則可能導致疾病。最有名的舉例為「亨丁頓舞蹈症」(Huntington's Disease)。正常人在第四對染色體上本來就帶有包含少於35個CAG重複出現的Huntingtin基因。然而亨丁頓舞蹈症患者的CAG序列重複大於37次。
重複出現的CAG會轉錄轉譯出蛋白質glutamine。而這類的病變不只出現在亨丁頓舞蹈症，有許多神經退化性的疾病也是由此相同的機轉造成，統稱為「Polyglutamine Diseases」。舉例如下：
另一群也三核苷酸重複序列擴張，但擴張序列並非CAG的疾病如下：
Reference:
1. Huntington's Outreach Project for Education at Stanford
http://web.stanford.edu/group/hopes/cgi-bin/hopes_test/trinucleotide-repeat-disorders/#sca1-spinocerebellar-ataxia-type-1
2. Di Prospero, Nicholas A., and Kenneth H. Fischbeck. "Therapeutics development for triplet repeat expansion diseases." Nature Reviews Genetics 6.10 (2005): 756-767.
重複出現的CAG會轉錄轉譯出蛋白質glutamine。而這類的病變不只出現在亨丁頓舞蹈症，有許多神經退化性的疾病也是由此相同的機轉造成，統稱為「Polyglutamine Diseases」。舉例如下：
- Huntington’s Disease (HD)
- SBMA (Spinobulbar Muscular Atrophy)
- SCA1 (Spinocerebellar Ataxia Type 1)
- SCA2 (Spinocerebellar Ataxia Type 2)
- SCA3 (Spinocerebellar Ataxia Type 3 or Machado-Joseph Disease)
- SCA6 (Spinocerebellar Ataxia Type 6)
- SCA7 (Spinocerebellar Ataxia Type 7)
另一群也三核苷酸重複序列擴張，但擴張序列並非CAG的疾病如下：
- Non-Polyglutamine Diseases
- Myotonic Dystrophy
- Fragile X Syndrome
- Friedreich’s Ataxia
- Spinocerebellar Ataxia Type 8, 12
Reference:
1. Huntington's Outreach Project for Education at Stanford
http://web.stanford.edu/group/hopes/cgi-bin/hopes_test/trinucleotide-repeat-disorders/#sca1-spinocerebellar-ataxia-type-1
2. Di Prospero, Nicholas A., and Kenneth H. Fischbeck. "Therapeutics development for triplet repeat expansion diseases." Nature Reviews Genetics 6.10 (2005): 756-767.
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