Genetic Diseases Flashcards
autosomal dominant diseases
- myotonic dystrophy 1
- achondroplasia
- neurofibromatosis
- HNPP
- Marfan syndrome
- polycystic kidney disease
- Huntington’s
- osteogenesis imperfecta
- charcot marie-tooth type 1A
autosomal recessive
- PKU
- ATD
- Tay-Sachs Disease
- Sandhoff Disease
- AB-variant of Tay-Sachs
- Sickle cell
- cystic fibrosis
- congenital adrenal hyperplasia
- 5-alpha reductase deficiency
x-linked dominant
-Fragile X syndrome
x-linked recessive
- Duchenne Muscular Dystrophy
- Hemophilia A
- testicular feminization
- dosage sensitive sex reversal
- Fabry disease
mitochondrial
- Kearns-Sayre
- MELAS
- MERRF
Duchenne muscular dystrophy
- Onset around 2 yrs, lose motor function, in wheelchair by 18 yrs, median age at death is 18 yrs; high CK levels, large calves
- deletions in many exons in Xp21.2 (dystrophin gene); nonsense frameshift
HNPP (hereditary neuropathy with liability to pressure palsies)
- limbs “go to sleep”
- Deletion of PMP22 gene due to unequal crossing over (PMP22 is integral glycoprotein in nerves)
osteogenesis imperfecta type 1
- Brittle bones, increased fractures, blue sclerae
- Loss of Function: nonsense frameshift in COL1A1 (important for collagen strength)
charcot-marie-tooth type 1A
- Demyelinating motor and sensory neuropathy
- Gain of Function: duplication of of PMP22 gene
osteogenesis imperfecta types 2,3,4
- Brittle bones, increased fractures, blue sclerae
- Novel Property Mutation: the COL1A2 protein has new property due to new/different folding, forming collagen trimers
Huntington’s disease
- Progressive neurodegenerative disorder with adult onset
- Polyglutamate disease; increased CAG repeats
- Parental transmission bias—trinucleotide expansion more likely to come from father
myotonic dystrophy
- Droopy eyes, intellectual difficulty, hypotonia
- Increased CTG repeats (in 3’ UTR) of DMPK gene
PKU
- Epilepsy, mental retardation, hyperactivity
- Defect in PAH-phenylalanine hydroxylase enzyme (common) or BH4 cofactor (rare, also have high neurotransmitter imbalance)
- high phenylalanine in blood
ATD (alpha1-antitrypsin deficiency)
- Late onset: increased risk of developing emphysema, liver cirrhosis/cancer
- Defective alpha1-AT protein (normally protease inhibitor of elastase; elastase recruited by neutrophil) increased elastase activity decreased elastin in lungs emphysema and lung damage
Tay Sachs
- Progressive neurodegeneration of CNS
- Screen enzyme activity (at low temp, both enzymes active, at high temp HexA degrades and B still functions) test and DNA test (three mutant alleles account for 95% of cases)
- Inability to degrade GM2 ganglioside, which aggregates in lysosomes
Sandhoff disease
- symptoms like Tay-Sachs
- Screening enzyme activity shows that both HexA and HexB are inactive (just Hex A in Tay-Sachs)
AB variant of Tay-Sachs
-HexA and HexB are normal but GM2 accumulates due to defect in the GM2 activator protein (GM2AP), which facilitates interaction between the lipid substrate and the HexA enzyme within the cell
cystic fibrosis
- thick, sticky mucus, frequent chest infections, and coughing or shortness of breath
- Mutation of CFTR gene; CFTR protein needed to regulate components of sweat, digestive juices, and mucus by regulating movement of chloride and sodium ion across epithelial membranes
achondroplasia
- rhizomelic limb shortening
- spinal cord compression; 3-7% die suddenly in during first year
- Gain of Function:Gly380Arg mutation in FGFR3 Gene (hot spot for mutation)
- incomplete dominance (homozygous is lethal)
neurofibromatosis type 1
- cafe au let spots, lisch nodules, neurofibromas
- 100% penetrance
- variable expressivity
- Mutation on chr. 17 on NF1 gene
marfan syndrome
- Connective tissue disorder
- risk of aortic aneurism
- tall and skinny
- Mutation in FBN1 mutations (codes for fibrillin)
Fragile X syndrome
- mental deficiency, dysmorphic facies, autism-like
- premutation can lead to FXTAS or premature ovarian failure
- Trinucleotide CGG expansion (>200 penetrant, hypermethylation)
- maternal gene anticipation
hemophilia A
- factor VIII deficiency (clotting)
- can supplement with factor VIII
Turner Syndrome
- 45X
- Gonadal dysgenesis, short stature, heart defects, fused kidneys, webbed neck, brown nevi, widely spaced nipple, infertility, social difficulty etc.
- meiotic nondisjunction
Klinefelter’s syndrome
- 47XXY
- Gonadal dysgenesis/hypogonadism, infertility, tall stature, gynecomastea, high frequency of sterility, language impairment
- meiotic nondisjunction, failure of recombination
XYY Syndrome
- usually fertile
- increased risk of behavioral and educational problems, delayed speech and language skills
- meiotic nondisjunction
- errors in paternal meiosis II (produce YY)