Table 1.
Nucleotide repeat disorders: disease gene characteristics
| Disease (abbreviation) | Gene | Normal repeat length | Expanded repeat length | Gene product | Repeat sequence | Location of repeat |
|---|---|---|---|---|---|---|
| Fragile X mental retardation 1, (Fragile X) | FMR1 | 5–55 | > 200 | Fragile X mental retardation protein | CGG•CCG | 5′ UTR |
| Friedreich’s ataxia (FRDA) | FXN | 5–34 | 66–1700 | Frataxin | GAA•CTT | Intron |
| Huntington’s disease (HD) | HTT | 6–35 | 36–250 | Huntingtin | CAG•CTG | Exon |
| Myotonic dystrophy type 1 (DM1) | DMPK | 5–34 | > 50 | Dystrophia myotonica protein kinase | CTG•CAG | 3′ UTR |
| Myotonic dystrophy type 2 (DM2) | CNBP | 11–26 | 75–11,000 | Cellular nucleic acid–binding protein | CCTG•CAGG | Intron |
| Spinal and bulbar muscular atrophy (SBMA) | AR | 9–34 | 38–68 | Androgen receptor | CAG•CTG | Exon |
| Spinal cerebellar ataxia type 1 (SCA1) | ATXN1 | 6–44 | 39–82 | Ataxin 1 | CAG•CTG | Exon |
| Spinal cerebellar ataxia type 2 (SCA2) | ATXN2 | 12–44 | 55–87 | Ataxin 2 | CAG•CTG | Exon |
| Spinal cerebellar ataxia type 3 (SCA3) | ATXN3 | 12–44 | 55–87 | Ataxin 3 | CAG•CTG | Exon |