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Flashcards in Specific Disorders Deck (20)
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1

Tay-Sachs

Autosomal Recessive Disorder.
Usually results in death by age 4.
Progressive deterioration of nerve cells and of the mental and physical abilities.
Creates harmful quantities of cell membrane components (gangliosides) which accumulate in the brain's nerve cells.
No known cure or treatment.
Mutation in HEXA gene on chromosome 15
Symptoms: ~6 months old; babies react strongly to loud noises "startle response," may also be listlessness or muscle stiffness (hypertonia)

2

Duchenne Muscular Dystrophy

X-linked recessive disorder
Affects 1 in 3,600 boys
Caused by a mutation in dystrophin
Symptoms usually appear by age 6
Early signs include enlargement of calves and deltoid muscles
By 10 - usually need braces to walk
By 12 - usually in a wheelchair
Progressive deterioration of muscles
Average life expectancy ~ 25 years old

3

Angelman Syndrome

- Genomic imprinting; chromosome 15
- Neuro-genetic disorder characterized by severe intellectual and developmental disability, sleep disturbance, seizures, jerky movements (especially hand-flapping), frequent laughter or smiling, and usually a happy demeanor.
- Caused by a deletion of or inactivation of genes in the maternally inherited chromosome 15. The maternal copy is imprinted (silenced) in this case.

4

Prader-Willi Syndrome

- Subset of Chromosome 15 (q11-13) are deleted or unexpressed on the paternal chromosome.
- Low muscle tone, short stature, incomplete sexual development, cognitive disabilities, problem behaviors, and a chronic feeling of hunger that can lead to excessive eating and life-threatening obesity.
- Incidence = between 1 in 25,000 and 1 in 10,000 live births
- Paternal copy of chromosome 15 imprinted (silenced)

5

Huntington's Disease

- Autosomal Dominant
- Neurodegenerative disorder that affects muscle coordination and leads to cognitive decline and behavioral symptoms.
- Noticeable in mid-adult life
- HD is the most common genetic cause of abnormal involuntary writhing movements (chorea)
- Gene mutated = Huntingtin; Expansion of a CAG triplet repeat stretch within the Huntingtin gene results in a different form of the protein which gradually damages cells in the brain through mechanisms not fully understood.
- HTT gene is located on the short arm of chromosome 4

6

Fabry Disease

- Genetic lysosomal storage disease
- X-linked recessive (not your typical X-linked recessive disorder though - females can exhibit symptoms just as severe as males)
- Deficiency of alpha galactosidase A
- Symptoms: Pain (hands and feet), renal involvement (kidney failure is possible), cardiac manifestations, angiokeratomas, lack of sweating (overheating = very common), clouding of the corneas
- Enzyme assay not a reliable diagnosis tool for females because of X-inactivation

7

Mucopolysaccharidosis (MPS)

- Lysosomal storage disorder
- Deficient in lysosomal enzymes needed to break down glycosaminoglycans
- Seven types

8

Xeroderma Pigmentosum

- Problem with nucleotide excision repair
- UV-induced skin cancer
- Caused by mutation in XP-A to XP-G
- Photosensitivity
- Pigmentation abnormalities
- Atrophic Skin
- >1000x increased risk of skin cancer
- 10x increased risk of internal tumors
- Neurological degeneration

9

Cockayne Syndrome

- Problem with transition-coupled repair
- Premature aging
- Caused by mutation in CSA or CSB
- Photosensitivity
- Growth failure
- Neurological abnormalities
- Retinal degeneration
- No skin cancer

10

Trichothiodystrophy

- Problem with transition-coupled repair
- Premature aging
- Caused by mutation XPB, XPD, or TTDA (subunits of basal transcription factor TFIIH)
- Photosensitivity
- Growth failure
- Neurological abnormalities
- Hair, nails, skin
- No skin canceer

11

Ataxia Telangiectasia

- Problem with DSB-R and checkpoint
- Leukemias and lymphomas
- Caused by a mutation in ATM
- Growth retardation
- Neurodegeneration (ataxia)
- Immunodeficiency
- Premature aging
- Radiation sensitivity
- Telangiectasias
- Infertility
- 40% develop cancer (leukemia, lymphoma and solid tumors)

12

AT-like Disorder

- Problem with DSB-R
- Ataxia

13

Nijmegen Breakage Syndrome

- Problem with DSB-R and checkpoint
- Lymphomas (usually B cells)
- Growth retardation
- Microcephaly and craniofacial dysmorphy
- immunodeficiency
- radiation sensitivity
- hypogonadism and infertility
- vitilgo and cutaneous sarcoidosis
- cancer (>50% of patients)

14

Werner's Syndrome

- Problem with telomere maintenance DSB-R
- Nonepithelial tumors

15

Bloom Syndrome

- Problem with DSB-R (replication repair) and ICL-R
- Epithelial tumors and leukemia

16

Rothmund-Thompson Syndrome

- Problem with TCR
- Osteosarcoma and skin cancer

17

Von Hippel–Lindau disease

- Rare autosomal dominant condition
- Predisposes individuals to benign and malignant tumors
- VHL results from a mutation in the von Hippel-Lindau tumor suppressor gene on chromosome 3p25.3

18

Beckwith-Wiedemann Syndrome

Imprinting disorder

19

Kennedy Disease

- Adult onset neurodegenerative syndrome affecting lower motor neurons
- CAG repeat expansion in exon1 (first N-terminal domain) of androgen receptor gene on X chromosome
- Female carriers do not have the disease
- The only CAG repeat expansion that is X-linked
- Normal: 9-34 repeats
- Reduced penetrance (males): 35-37 repeats
- Full penetrance (males): 38+ repeats

20

Pallister-Killian Syndrome

12p extra piece of chromosome