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Medical Genetics
Exam 1
88
Other
Professional
09/23/2013

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Term
AAV vector
Definition
Pro: high titer, non-toxic
Con: small genome, non-integrating
Target: muscle, liver, brain
Term
Achondroplasia
Definition
big forehead and short limbs
autosomal dominant
lethal in utero to homozygotes
most common form of dwarfism
gain of function in FGFR3 gene
inhibits bone growth
Term
Adenovirus vector
Definition
Pro: high titer, cycling independent
Con: non-integrating, immune reaction
Target: cancer, immunization
Term
Angelman Syndrome
Definition
genetic imprinting
metnal retardation, seizures, "happy puppet syndrome",
maternal deletion with paternal imprinted on chromosome 15
Term
Becker Muscular Dystrophy
Definition
allelic with DMD, less severe, later onset, in-frame mutations, shortened-partially-functional protein
Term
Beckwith-Wiedemann Syndrome
Definition
example of a syndrome defect
heterogenous overgrowth (fat baby)
both IGF2 genes are expressed (maternal is normally imprinted)
normal intelligence, increased risk of tumors
Term
Biotinidase deficiency
Definition
Symptoms: alopecia (loss of hair), ataxia, seizures, deafness, blindness, hypoglycemia, hyperammonemia, acidosis, late childhood or adolescence
Inheritance: autosomal recessive, esp. French Canadians
Biochemical: cannot release biotin from proteins for recycle, biotin is cofactor for 4 hydroxylase
Treatment: newborn screening, biotin daily
Term
Breast cancer
Risk, risk related genes
Definition
Risk in women 1/8
BRCA1: 50-80% breast, 40-60% multifocal brest, 15-45% ovarian
BRCA2: 50-85% breast, 10-20% ovarian, 6% male breast
Term
CYP2C9
Definition
Metabolizes wafarin/coumadin
Related to VKORC1 gene inhibition
Term
Charcot-Marie-Tooth (CMT) disease, type 1
Definition
Symptoms: distal wasting and weakness, loss of reflexes, loss of sensation, onion-bulb
Inheritance: autosomal dominant, duplication of struture protein for PNS myelin (PMP-22)
Biochemical: segmental demyelination of neurons, altered nerve velocity,
Term
Cystic fibrosis
Definition
Symptoms: neonatal onset, elevated sweat chloride, chronic cough, fatty stools, jaundice, clubbing, lung disease and liver failure
Inheritance: autosomal recessive (esp. Caucasian), allelic heterogeneity
CFTR gene (cAMP activated chloride channel), commonly delta-F508 deletion of Phe; plymorphisms of intron 8 (9Ts normal, 5Ts CF)
Biochemical: effects outwardly retifying chloride channels and a sodium channel; delta-F508 has abnormal protein folding -> impaired protein trafficking
Treatment: depends on type of defect
Term
Cytochrome P450 2D6 (CYP2D6)
Definition
Metabolizes codeine to morphine
Term
DS positive tests
Definition
Low AFP, low uE3, high hCG, high inhibin, low PPAP-A in first trimester
Term
Duchenne Muscular Dystrophy
Definition
Symptoms: 3-6years onset, muscle wasting, Gower sign (rise with press on thighs), walk on toes, pseudo-hypertrophy of calves, resp. or cardiac failure, elevated creatine kinase
Inheritance: x-linked recessive, 33% new mutations, 15% germline mosaic of mom, DMD gene
Biochemical: dystrophin protein part of muscle and neuron cytoskeleton and ECM
Term
Ectrodactyly
Definition
split hand deformity
locus heterogeneity
reduced penetrance (80%)
Term
Edwards syndrime Tri 18 positive tests
Definition
Low AFP, low uE3, low hCG, low PPAP-A
Term
Ehlers Danlos Syndrome
Definition
skin hyperextensibility
different mutations at different loci
auto dom, auto rec, X-linked
Term
Epigentics cancer
Definition
DNA hypomethylation: microsatelite instability, oncogene activation, loss of imprinting
X-chromosome inactivation
DNA Hypermethylation: silence tumor suppressor gene
Term
Familial Hypercholesterolemia
Definition
more severe if homozygous
lots of cholesterol (shows up earlier)
xanthomas (deposits of cholesterol in skin and tendons)
Term
Family adenomatous polyposis (FAP)
Apdenomatous polyposis coli (APC)
Definition
Symptoms: benign adenomatous polyps in first two decades, one(+) polyp malignant
Inheritance: auto dom, APC (tumor supressor gene)
Biochemical: beta catenin activated w/o APC, more proliferative gene expression
Treat: remove colon
Term
Fetal Alcohol Syndrome
Definition
growth deficiency, brain malformation, short palpebral fissures, thin upper lip, smooth philtrum, behavior problems
tetratology related
Term
Fragile-X syndrome
Definition
Symptoms: mental retardation, large head, prominent jaw after puberty, large testes, autistic features
Inheritance: triplet nucleotide expansion of FMR1, normal transmitting males (carriers with normal pheno); 50-200 repeats prrmutation, >200 repeats mutant, mostly maternal transmission
Biochemical: loss of function of FMRP involved in mRNA transport in neural cells
Term
Galactosemia
Definition
Symptoms: vomiting and refusal to fee after first milk, liver disease, lethargy, cataracts, sepsis
Inheritance: autosomal recessive, locus heterogeneity, GALT mutation (Gln188Arg, missense, inactive protein); Duarte allele (Asn314Asp, 50% activity)
Biochemical: deficiency of galactose 1-P uridyltransferase (GALT), glactokinase (cataracts only) or epimerase; high levels of galactose is toxic
Treatment: galatactose-free diet (lactose-free formula)
Term
HNCPP
Hereditary non-polyposis colon cancer
(Lynch syndrome)
Definition
Symptoms:
Inheritance: auto dom, 5-10% CRC, 80% penetrance, late onset, mutant mismatch repair genes, LOH
Biochemical: microsatellite instability, increased rate of mutations
Term
HNPP
Definition
Hereditary neuropathy with liability to pressure palsies
Symptoms: episodic numbess, atrophy with minor trauma
Inheritance: deletion of PMP-22
Term
Hardy-Weinburg Equilibrium
Definition
p2+2pq+q2=total
Term
Hemophilia A
Definition
Symptoms: frequent bleeding, bleeding to joints
Inheritance: x-linked recessive, clotting factor VII gene, often inversion type mutation
Biochemical: minor symptoms with 5% activity, full disease <1% activity
Term
Herpes vector
Definition
Pro: high titer, large genome
Con: non-integrating, ? Toxicity
Target: CNS, cancer
Term
Holoprosencephaly
Definition
failure of midface and forebrain to develop well
most common congenital brain defect
lots of causes, hedgehodge mutation
Term
Homocysturnia
Definition
Symptoms: long/thin habitus, downward lens dislocation, thomboembolism, joints are tight
Inheritance: autosomal recessive with locus heterogeneity
Biochemical effect: deficiency/loss of cystathionine synthase (converts homocystein to cystathionine, uses pyridoxal phosphate cofactor)
results in excess homocysteine and impairs disulfide bridging of FBN1
Treatment: vitamin therapy and pyridoxine used as treatments, betaine (covert homocystein to methionine)
Term
Huntington disease
Definition
Symptoms: progressive abnormalities, involuntary movements, agression, apathy, psychosis, 15-18 yrs post-dx
Inheritance: autosomal dominant, late onset, expanded repeat in HTT gene coding region, few new mutations, 40-55 repeats = late onset, >60 = juvenile onset
Biochemical: Huntingtin protein accumulates in nucleus with gain of function affecting rate of neuron decay
Term
Indiana new born screening
Definition
PKu, galactosemia, maple syrup urine disease, homocystinuria, biotinidase deficiency, hypothyroidism, congenital adrenal hyperplasia, cystic fibrosis, and sickle cell anemia
Term
Leber hereditary optic neuropathy (LHON)
Definition
disease of mitochondria
results in blindness due to optic nerve degeneration
Term
Lentivirus vector
Definition
Pro: integrates, non-toxic
Con: insertional mutagenesis
Target: bone marrow, other stem cells, T cells
Term
Lesch-Nyhan Syndrome
Definition
Symptoms: red-orange sand in diapers, hyperuricemia, self-mutilation, gout, kidney stones
Inheritance: x-linked recessive
Biochemical: deficiency of HPRT (part of purine salvage), buildup of (hypo)xanthine and uric acid
Treat: allopurinol (prevent uric acid build up)
Term
Maple syrup urine disease (MSUD)
Definition
Symptoms: normal at birth, first week of life -> lethargy, weight loss, acidosis, hyperammonemia, sweet urine odor
Inheritance: autosomal recessive
Biochemical: deficiency of BCKA DH (6 gene complex), accumulation of BCAA and BCKA --> ketoacidosis and neurological toxicity
Treatment: diet low in leucine, regular monitor Leu, Iso, Val; liver transplant
Term
Marfan syndrome
Definition
tall/thin, large hands and long thin fingers
upward lens dislocation
dissecting aneurysms, valvular incompetence
autosomal dominant with pleiotropy and variable expressivity, heterogeneity
defect in Fibrillin-1 gene (glycoprotein of microfibrils in ECM)
25-35% de novo mutations
haploinsufficiency and dominant-negative effects
overactivity of TGF-beta from lack of FBN1
Term
Myotonic dystrophy
Definition
Symptoms: progessive muscle wasting (begins in face), unable to relax after contract (myotonia), early cataracts
Inheritance: autosomal dominant, anticipation, DMPK gene (inc. repeats in 3' noncoding region), trans dominant RNA
Biochmical: extra repeats cause wtong splicing 9 of a chloride channel -> hyperexcitability of skeletal m.,
Term
Neural tube defects
Definition
largest impact of single malformations
Term
Neurofibromatosis 1
Definition
Symptoms: multiple fleshy tumors in skin, cafe-au-lait spots, lisch nodules,
Inheritance: autosomal dominant, variable expressivity, pleiotropic (affects many tissues), allelic heterogeneity, loss of heterogeneity
Term
Newborn Screening Criteria
Definition
1. well defined and high population frequency
2. w/o treatment has high morbidity/mortality
3. treatment/intervention available
4. asymptomatic at early stages
5. rapid, inexpensive, specific, highly sensitive test
6. public health infrastructure
Term
Osteogenesis Imperfecta Type II
Definition
autosomal dominant, mostly new mutations
brittle bones, large unmineralized skull
perinatal lethal
Term
Parder Willi
Definition
genetic imprinting
mental retardation, hypotonia, short stature, compulsive overeating, obesity
parental deletion with maternal imprint on chromosome 15
Term
Phenylketonuria
Definition
Symptoms: mousy body odor/urine, hyperyphenylalnienemia, developmental delays, microcephaly, fair skin, eczema
Inheritance: autosomal recessive, allelic heterogeneity (likely compound heterozygotes), locus heterogeneity
Biochemical: deficiency of phenylalanine hydroxylase (converts phenylalanine to tyrosine, uses BH4 as cofactor); high Phe levels inhbits transport of neutral aa across BBB
Treatment: screening (onset by 6 months, has already effected mental development), dietary Phe restriction, lifetime
Term
Polycystic kidney disease
Definition
Symptoms: bilateral kidney cysts, hypertension, blood in urine, kidney stones
Inheritance: autodomal dominant, late onset, mutations in PKD1, allelic heterogeneity, second hit needed
Term
Retrovirus vector
Definition
Pro: integrates, non-toxic
Con: insertional mutagenesis
Target: bone marrow, other stem cells, T cells
Term
Rett syndrome
Definition
Symptoms: onset 6-18 months, slow head growth, loss of milestones, washing/wringing/squeezing hands
Inheritance: x-linked dominance, variable expressivity, most sporadic paternal mutation to MeCP2
Biochemical: loss of MeCP2 leads to inappropriate expression of genes
Term
Robin Sequence
Definition
a sequence defect
U-shaped cleft palate and small mandible
Term
Sonic hedgehod gene
Definition
developmental regulatory gene
Term
Thiopurine methyltransferase (TPMT)
Definition
Metabolizes thoopurine class of chemotherapies
Term
Van der Woude Syndrome
Definition
cleft lip and possible cleft palate and/or lip pits
reduced penetrance
Term
Waardenburg Syndrome
Definition
variable expressive
white forelock
Term
allelic heterogeneity
Definition
number of different alleles at same locus give same physical phenotype
most diseases
Term
anticipation
Definition
Phenomenon where there is progressively earlier onset and/or increased severity of disease with successive family generations
Ex: mytonic dystrophy
Term
association defect
Definition
type of multiple birth defects
low frequency clustering of defects but no clear connection between them
Term
autosomal dominant disorders
Definition
Huntingon, Alzheimer, Neurofibromatosis, Marfan, Hypercholesterolemia, Myotonic dystrophy, PCKD, Achondroplasia
Term
autosomal recessive diseases
Definition
Cystic Fibrosis, congenital deafness, Tay-Sachs, Sickle cell, Phenyltonuria
Term
carrier frequency (recessive)
Definition
2q
Term
compound heterozygote
Definition
2 different mutant allele's at same locus
Term
congenital rubella
Definition
heart defects, hearing loos, eye abnormalities
"Blueberry muffine baby"
mother infected, pass to baby
Term
consanguinity
Definition
inbreeding, increased chances of getting autosomal recessive disease
Term
deformation
Definition
type of single birth defect
mechanical stress to normal tissue
altered form like a dent in the skull
Term
disruption
Definition
type of single birth defect
breakdown of normal tissues
necrosis, amputation by amniotic band
Term
dysmorphology
Definition
abnormal shape or form
Term
dysplasia
Definition
type of single birth defect
abnormal developmetn of specific fetal tissue
ex: achondroplasia
Term
genetic bottleneck
Definition
when germ cells are made they pick up a couple mitochondria at random to make an oocyte
those mitochondria are then amplified
few selected, then multiplied greatly
Term
genetic imprinting
Definition
one allele on and the other is off
certain genes from mother or father are turned off
Term
germline mosaicism
Definition
gonad cells, multiple gametes can inherit mutation and pass along
parent unaffected with multiple affected offspring
ex: Neurofibromatosis 1
Term
heterodisomy
Definition
two different homologs from same parent
Term
heteroplasmy
Definition
cell whose mtDNA is different
Term
homoplasmy
Definition
cell whose mtDNA is identical
Term
isodisomy
Definition
two copies of same homolog from same parent
Term
late-age onset diseases
Definition
Huntington, Alzheimer, Breast cancer
Term
locus heterogeneity
Definition
mutations at different loci give same clinical phenotypes
ex: Ehlers Danlos Syndrome
Term
lyonization
Definition
skewed x-inactivation
one X inactivated early in embryo
same X inactivated in descendant cells
Term
malformation
Definition
type of single birth defect
disorder of tissue development
usually during first trimester
Term
mosaicism
Definition
individual or tissue can have two different sets of genes in their cells
Term
penetrance
Definition
not all individuals with disease present with clinical symptoms
#affected/totalwithmutation
Term
sequence defect
Definition
type of multiple birth defects
single anomaly that cascades and causes a bunch of other anomalies
Term
sex-linked inheritance
Definition
phenotypic expression of an allele related to the chromosomal sex of the individual
Term
somatic mosaicism
Definition
most cells normal, but one line of offspring of cells has mutation
non-inheritable effects
Term
syndrome defect
Definition
type of multiple birth defects
recognized pattern of defects from a specific genetic etiology
ex: Down syndrome
Term
tetratology
Definition
study of birth defects and their causes
several factors determine a specific sitmulus's tetratologenicity
Term
threshold effect
Definition
if enough mitochondria in a cell have mutant alleles, then the cell will be symptomatic
Term
uniparental disomy
Definition
both homologs of a chromosome pair come from the same parent
nondisjunction during meiosis
Term
variable expressivity
Definition
the expression of the disease is variable between individuals
common to genes that affect multiple systems
Ex: Waardenburg Syndome
Term
x-linked dominant
Definition
seen more often in females
Term
x-linked recessive
Definition
more often found in males
ex: color blindness
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