Term
|
Definition
| Asymptomatic, but unstable, with a tendency to expand in the next generation |
|
|
Term
|
Definition
| Tendency toward earlier age of onset and/or greater severity in each subsequent generation, due to progressive expansion of the repeat length |
|
|
Term
| Clinical Presentation - Fragile X syndrome |
|
Definition
1. Developmental delay, mental retardation
2. Sometimes presents with autism, ADD
3. Dysmorphic features
4. Some late-onset features in permutation carriers: ovarian failure, ataxia |
|
|
Term
| Clinical Presentation - Myotonic dystrophy |
|
Definition
1. Myotonia, muscular dystrophy
2. Cataracts, hypogonadism, frontal balding |
|
|
Term
| Clinical Presentation - Friedreich ataxia |
|
Definition
1. Gait incoordination in childhood
2. Ataxia, absent reflexes
3. Cardiomyopathy
4. Intellectual decline |
|
|
Term
| Clinical Presentation - Huntington disease |
|
Definition
1. Middle-age onset
2. Choreoathetosis
3. Dementia, psychosis |
|
|
Term
|
Definition
Fragile X: X-linked recessive/semi-dominant
Myotonic dystrophy: autosomal dominant
Friedreich ataxia: autosomal recessive
Huntington disease: autosomal dominant |
|
|
Term
|
Definition
1. CGG repeat in 5'-untraslated region, near promoter
2. Premutation and full mutation alleles
3. Premutation expands when inherited from the mother
4. Full mutation must also be hypermethylated to cause disease |
|
|
Term
| Mech - Myotonic dystrophy |
|
Definition
1. CTG repeat in 3'-untranslated region
2. Mild and severe forms based on length repeat
3. Greatest expansions occur when inherited from the mother; can produce severe neonatal form |
|
|
Term
|
Definition
1. GAA repeat in an intron
2. Small proportion of patients are compound heterozygotes with an expansion on one allel and a point mutation on the other |
|
|
Term
| Mech - Huntington disease |
|
Definition
1. CAG repeat in an exon
2. Codes for polyglutamine tract in the protein product
3. Length of repeat inversely related to age of onset
4. Greatest expansions occur when inherited from the father |
|
|
