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Flashcards in Genetic diseases Deck (31):

What are some examples of autosomal dominant diseases?

- Huntington disease
- Myotonic dystrophy
- Polycystic kidney disease
- Ehlers Danlos syndrome


What is Ehlers Danlos syndrome and what is its cause?

- Connective tissue disorder.
- Symptoms include:
1. Bruising easily
2. Thin skin
3. Fragile blood vessels
4. Easily damageable hollow organ
- Caused by mutations in collagen gene (esp. COL3A1)


What are some examples of autosomal recessive diseases?

1. Cystic fibrosis
2. Spinal muscular atrophy
3. Congenital adrenal hyperplasia


What are some examples of numerical abnormalities?

- Turner syndrome: XO
- Down syndrome: Trisomy 21
- Edward's syndrome: Trisomy 18


What is the cause of Down syndrome?

- Trisomy 21
- Result of chromosome non-disjunction
- Most commonly occurs during meiosis, especially during egg formation
- >90% of cases inherited maternally
- Risk of non-disjunction and thus acquiring the disease increases as maternal age increases


What is an example of disease causing insertion/deletion?

- 22q.11.2 deletion syndrome.
- Causes schizophrenia and other associated neurological disorders.
- Causes DeGeorge's syndrome.


What is an example of disease causing reciprocal translocation?

- Philadelphia chromosome.
- Balanced translocation between chromosomes 9 and 22.
- Found in ~95% of patients with chronic myeloid leukaemia.


What are the common genetic disorders caused by sex chromosome non-disjunction?

1. Turner's syndrome (45 XO)
2. Klinefelter's syndrome (47 XXY)
3. XYY male


What are the symptoms of Turner's syndrome?

- Webbed neck
- Short
- Infertility


What are the symptoms of Klinefelter's syndrome?

- Tall and thin
- Gynecomastia
- Learning impairment (mild)
- Infertility


What are examples of X-linked recessive disorders?

1. Duchenne muscular dystrophy
2. Haemophilia
3. Red-green colour blindness


What are the causes and symptoms of DMD?

- Mutation in Dystrophin gene on X-chromosome
- Progressive muscle weakness and degeneration


What are the causes and symptoms haemophilia?

- Haemophilia A: Factor VIII affected
- Haemophilia B: Factor IX affected
- Ineffective blood clot formation results in excessive bleeding.


What is an example of an X-linked dominant disorder?

- Rett syndrome.
- Caused by a mutation in MeCP2 gene, which makes protein involved in methylation.
- Associated with neurological disorders such as seizures, inability to talk and hand movements.


What is Campomelic Dysplasia?

- Mutation of SOX9 gene on chromosome 17.
- Causes sex reversal and skeletal dysplasia in males.


What are the diseases associated with maternal uniparental disomy?

- 7: Silver-Russell syndrome
- 11: Silver-Russell syndrome
- 14: Maternal UPD14 syndrome (Temple syndrome)
- 15: Prader-Willi syndrome


What are the diseases associated with paternal uniparental disomy?

- 6: Transient neonatal diabetes
- 11: Beckwith-Weidemann syndrome
- 14: Paternal UPD14 syndrome (Kagami-Wang syndrome)
- 15: Angelman syndrome


What is Beckwith-Weidemann syndrome?

- Paternal uniparental disomy of chromosome 11.
- Foetal overgrowth with increased risk of childhood tumours.
- Overexpression of IGF2 in placental cells (paternal).
- No expression of CDKN1C (maternal).


What is Angelman syndrome?

- Paternal uniparental disomy 15.
- Severe developmental delays.
- Ataxic movement.
- Short attention spans.
- No expression of UBE3A.


What is Silver-Russell syndrome?

- Maternal uniparental disomy 7/11.
- Slow pre-/postnatal growth.


What is Prader-Willi syndrome?

- Maternal uniparental disomy 15.
- Neurological problems such as hypotonia, respiratory difficulties, sleeping disorders...
- Excess weight gain
- Delayed weight gain


What are examples of mitochondrial diseases?

2. Kearns-Sayre syndrome


What are examples of trinucleotide expansion diseases?

- Fragile-X syndrome: Caused by CGG repeat
- Myotonic dystrophy: Caused by CTG repeat
- Huntington disease: Casued by CAG repeat
- Friedreich ataxia: Caused by GAA repeat


What causes fragile-X syndrome?

- CGG repeat on exon 1 of FMR1 gene on X-chromosome.
- TNEs prevent the FMR1 gene from being transcribed, preventing the production of FMRP, which is essential in cognitive development.


What are the symptoms of fragile-X syndrome?

- Learning disabilities
- Long face/large ears
- Increased risk of seizures
- Autism


What causes Friedreich's ataxia?

- GAA repeats on intron 1 of Frataxin gene on chromosome 9.
- Trinucleotide repeats cause increased epigenetic modifications (including histone modifications) to the Frataxin gene, suppressing its transcription and expression.


What are the symptoms of Freidreich's ataxia?

1. Speech and movement abnormalities
2. Heart disease
3. Diabetes


What causes myotonic dystrophy?

- CTG repeats on 3’ end of DMPK gene in chromosome 19.
- Accumulation of abnormal pre-mRNA sequesters RNA-binding proteins and prevents them from carrying out their normal functions (alternative splicing).


What are the symptoms of myotonic dystrophy?

1. Progressive muscular dystrophy
2. Myotonia (difficulty relaxing muscles post-contraction)


What causes Huntington's disease?

- CAG repeats in Huntingtin gene in chromosome 4.
- CAG repeats sequence causes polyQ (Gln) strand in Huntingtin protein.
- PolyQ sequences in Huntingtin gene cause formation of polyQ-huntingtin aggregates when the protein is cleaved.
- Aggregates damage mitochondria, leading to the stimulation of apoptosis.


What are the symptoms of Huntington's disease?

1. Intellectual decline
2. Myoclonus
3. Dystonia
4. Dementia