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160 Cards in this Set
- Front
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Genetic term for when neither of 2 alleles is dominant.
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Codominance
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Genetic term for when the nature and severity of the phenotype varies between individuals.
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Variable expression
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Genetic term for when not all individuals with a mutant genotype show the mutant phenotype.
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Incomplete penetrance
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Genetic term for when one gene has more than one effect on a person's phenotype.
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Pleiotropy
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Genetic term describing when differences in phenotype depend on whether the mutation was maternal or paternal.
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Imprinting
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Give an example of genetic imprinting.
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Angelman syndrome (maternal) vs. Prader-Willi syndrome (paternal). Can also happen if uniparental disomy.
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Genetic term for when the severity of disease worsens OR age of onset is earlier in succeeding generations.
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Anticipation.
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Give an example of codominance.
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ABO blood types, alpha-1 antitrypsin deficiency.
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Give an example of genetic anticipation.
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Any trinucleotide repeat disease, i.e. Huntington's disease, myotonic dystrophy, Friedrich's ataxia, fragile X syndrome.
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When the patient inherits a mutation in a tumor suppressor gene, but the complementary allele must be deleted/mutated before cancer develops.
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Loss of heterozygosity (aka two-hit hypothesis). Note: this is NOT true of oncogenes, only of tumor suppressor genes like Rb.
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An example of loss of heterozygosity (two-hit hypothesis).
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Retinoblastoma (Rb1)
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When a heterozygote produces a nonfunctional altered protein that also prevents the normal gene product from functioning.
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Dominant negative mutation.
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When certain alleles at 2 linked loci tend to occur together more often than chance.
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Linkage disequilibrium
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Genetic term for when different cells in the body have different genetic makeup.
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Mosaicism
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Genetic term for when mutations at different loci produce the same phenotype.
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Locus heterogeneity
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An example of locus heterogeneity.
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Albinism
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An example of mosaicism
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Random X inactivation in females-lyonization (normal). Can also happen in trisomies like Down Syndrome.
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When there is presence of both normal and mutated mtDNA, resulting in variable expression in mitochondrial inherited diseases.
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Heteroplasmy
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When the offspring receives 2 copies of a chromosome from 1 parent and no copies from the other.
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Uniparental disomy
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The Hardy-Weinberg equilibrium equation for population genetics.
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Disease prevalence: p2 + 2pq + q2 = 1, with allele prevalence of p+q=1. The heterozygote prevalence is 2pq. The prevalence for X-linked recessive disease = q (males) or q2 (females).
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4 assumptions of the Hardy-Weinberg equilibrium.
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No new mutation, no selection, no migration, random mating.
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At a gene locus, how is the non-active allele inactivated?
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Methylation
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A disease of mental retardation, obesity, hypogonadism and hypotonia, which is an example of genetic imprinting (paternal mutation).
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Prader-Willi syndrome
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A disease of mental retardation, seizures, ataxia, and inappropriate laughter, and an example of genetic imprinting (maternal mutation).
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Angelman syndrome
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A mode of inheritance that affects males and females equally in many generations, and often presents after puberty. Often pleiotropic and due to a defect of a structural gene.
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Autosomal dominant
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A mode of inheritance that is often due to an enzyme deficiency and usually presents in childhood. 25% of offspring from 2 carriers have the disease.
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Autosomal recessive--often more severe than autosomal dominant diseases.
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Sons of heterozygote mothers have a 50% chance of being affected (a disease of nephews and uncles). More severe in males, no male-male transmission.
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X-linked recessive
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A mode of inheritance transmitted by either parent. Mothers transmit the disease to either sons or daughters, fathers always transmit it to daughters only.
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X-linked dominant
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An example of an X-linked dominant disease.
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Hypophosphatemic rickets
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How is a disease of mitochondrial inheritance transmitted?
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From the mother only, and ALL of her children may show signs of the disease.
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Give an example of mitochondrial inheritance.
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Leber's hereditary optic neuropathy (LHON), mitochondrial myopathies (MELAS, MERRF)
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Name the gene and chromosome affected in adult polycystic kidney disease.
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APKD1, chromosome 16
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Symptoms of adult polycystic kidney disease
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Pain, hematuria, hypertension, progressive renal failure. Bilateral enlarged kidneys with many large cyts.
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Mode of inheritance of juvenile polycystic kidney disease.
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Autosomal recessive.
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Some extrarenal manifestations of adult polycystic kidney disease.
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Hepatic cysts (most common), berry aneurysms, mitral valve prolapse.
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Symptoms of familial hypercholesterolemia (aka hyperlipidemia type Iia).
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Cholesterol >700 mg/dl, severe and early atherosclerotic disease, tendon (esp. Achilles) xanthomas. MI before age 20. Heterozygotes (1:500) have cholesterol ~300 mg/dl.
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Mechanism of elevated LDL in familial hypercholesterolemia.
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Defective or absent LDL receptor
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Mechanism of Marfan syndrome
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Fibrillin gene mutation causing connective tissue disorders
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Three organs/systems affected by Marfan syndrome
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SKELETAL (tall, long extremities, pectus excavatum, hyperextensive joints, long, tapering fingers and toes), CARDIAC (cystic medial necrosis of the aorta causing aortic incompetence and dissecting aortic aneurysms; floppy mitral valve), OCULAR (subluxation of the lenses)
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Symptoms of neurofibromatosis type 1 (von Recklinghausen's disease)
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Café-au-lait spots, neural tumors, Lisch nodules (pigmented iris hamartomas), skeletal problems (scoliosis), optic pathway gliomas, pheochromocytoma, increased tumor susceptibility. NOT associated with bilateral acoustic neuroma (that is NF-2).
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Name the chromosome for NF-1
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Chromosome 17 (17 letters in von Recklinghausen)
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Name the chromosome for NF-2
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Chromosome 22 (for type 2)
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Symptoms of neurofibromatosis type 2
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Bilateral acoustic neuroma, juvenile cataracts
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Symptoms of tuberous sclerosis
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Sebaceous adenomas on face, hypopigmented ash leaf spots on skin, cortical and retinal hamartomas, seizures, mental retardation, renal cysts, renal angiomyolipomas, cardiac rhabdomyomas, risk for astrocytoma.
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Name an autosomal dominant disorder associated with an increased risk for renal cell carcinoma, and another one with an increased risk of renal angiomyolipoma.
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RCC-von Hippel-Lindau (50% of patients). Angiomyolipoma-tuberous sclerosis.
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A disorder of hemangioblastomas of the retina, cerebellum, and/or medulla.
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von Hippel-Lindau disease
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Name the gene and chromosome for von Hippel-Lindau disease.
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VHL gene, chromosome 3p (3 words in vHL)
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Name an autosomal dominant disorder associated with an increased risk for astrocytoma, and another one with an increased risk of hemangioblastoma.
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Astrocytoma: tuberous sclerosis, hemangioblastoma: vHL
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A 40-year-old patient presents with depression, progressive dementia, and choreiform movements. What is the disease?
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Huntington's disease
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What neuroanatomic and neurochemical changes happen in Huntington's disease?
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Caudate atrophy and decreased levels of ACh and GABA in the brain. Triplet (CAG) repeats.
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On what chromosome is the gene for Huntington's disease?
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Chromosome 4 (hunting 4 food)
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A 20-year-old patient presents with adenomatous polyps covering the colon. She develops colon cancer. What is the disease?
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Familial adenomatous polyposis
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What are the gene and chromosome involved in familial adenomatous polyposis?
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APC gene, chromosome 5 (5 letters in polyp)
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A patient presents with spheroid erythrocytes, hemolytic anemia, and increased MCHC. He is cured with a splenectomy. What is the disease and its inheritance?
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Hereditary spherocytosis (autosomal dominant)
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What autosomal dominant disease results in dwarfism (short limbs, but head and trunk normal size)?
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Achondroplasia
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What is the cellular defect associated with achondroplasia?
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Cell-signaling defect of fibroblast growth factor (FGF) 3
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What increases the risk of achondroplasia?
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Advanced paternal age.
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Give some examples of autosomal recessive diseases.
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Cystic fibrosis, albinism, PKU, thalassemias, sickle cell anemia, glycogen storage diseases, mycopolysaccharidoses (except Hunter's-XR), sphingolipidoses (except Fabry's-XR), infant polycystic kidney disease, hemochromatosis.
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A baby presents with meconium ileus, bronchiectasis, steatorrhea, and failure to thrive. What test do you order?
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A sweat test for cystic fibrosis. (Baby would have increased concentration of Cl- ions.)
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Name four major organ systems affected by cystic fibrosis.
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LUNGS (thick mucus, bronchitis, bronchiectasis, recurrent pulmonary infections), GI (pancreatic insufficiency, meconium ileus, steatorrhea), REPRODUCTIVE (male infertility d/t bilateral absence of vas deferens)
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What vitamins are deficient in cystic fibrosis?
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A,D,E,K
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What gene and chromosome are involved in cystic fibrosis?
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CFTR gene on chromosome 7 (deletion of Phe 508)
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What is the function of the CFTR gene normally?
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Secrete Cl- into the lungs and GI tract and actively reabsorb Cl- from sweat.
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What is the most common lethal genetic disease of Caucasians?
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Cystic fibrosis
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Name a major treatment for cystic fibrosis.
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N-acetylcysteine to loosen mucous plugs.
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Are female carriers of X-lined recessive disorders affected by the disease? Why or why not?
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They are rarely affected because of random X inactivation.
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Give some examples of X-lined recessive disorders.
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Bruton's agammaglobulinemia, Wiskott-Aldrich syndrome, Fragile X, G6PD deficiency, Ocular albinism, Lesch-Nyhan syndrome, Duchenne's muscular dystrophy, Hemophilia A and B, Fabry's disease, Hunter's syndrome.
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What is the mechanism of the defect involved in Duchenne's muscular dystrophy?
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A frame-shift mutation causes a deletion of the dystrophin gene (and protein). There is accelerated muscle breakdown.
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A 3-year-old boy develops weakness in the pelvic girdle muscles, pseudohypertrophy of the calf muscles, and cardiac myopathy. What is the disease?
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Duchenne's muscular dystrophy
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What is Gower's maneuver?
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When a patient requires assistance from the upper extremities to stand up (a sign of proximal limb weakness seen in muscular dystrophy).
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How is Becker's muscular dystrophy different than Duchenne's?
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The dystrophin gene is mutated, not deleted, and the disease has a later onset. Both diseases, however, are XR.
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A boy presents with mental retardation/autism, and enlarged testes, jaw and ears. What X-linked disease does he have?
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Fragile X syndrome (eXtra-large testes, jaw and ears)
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What gene is defective in fragile X syndrome?
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Defective methylation and expression of the FMR1 gene. Fragile X syndrome is also associated with chromosomal breakage and trinucleotide repeats.
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What X-linked recessive disease is the 2nd most common cause of genetic mental retardation (behind Down syndrome)?
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Fragile X syndrome
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Name the 4 trinucleotide repeat diseases.
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Huntington's disease, myotonic dystrophy, Friedrich's ataxia, Fragile X syndrome
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Name the 3 autosomal trisomies and their relative incidence.
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Trisomy 21 (Down) > Trisomy 18 (Edward's) > Trisomy 13 (Patau's)
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What results would be expected on prenatal screening for Down syndrome?
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Decreased alpha-fetoprotein, increased beta-hCG, increased nuchal translucency
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For what other diseases are Down syndrome patients at risk?
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ALL, Alzheimer's disease after age 35
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What is the life expectancy for patients with Edwards' and Patau's syndromes?
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<1 year
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What is the life expectancy for Down syndrome?
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45-50 years
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What is the most common cause of genetic mental retardation in America?
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Down syndrome
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How can you tell Edwards' syndrome and Patau's syndrome apart?
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Edwards': micrognathia, low-set ears, clenched hands. Patau's: microcephaly, cleft lip/palate, polydactyly (more severe defects). Both have rocker-bottom feet, severe mental retardation, and heart defects.
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What type of cardiac defects do Down syndrome patients have?
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Endocardial cushion defects, especially septum primum-type ASD
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If meiotic nondisjunction occurs, under what circumstances could normal gametes still be produced?
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If the nondisjunction happened in anaphase II, 50% of the gametes are affected (50% are normal). If it happened in anaphase I, half of the gametes would have an extra chromosome, and the other half would have no chromosome. See 2008 FA chart, p 119.
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Which chromosomal inversion (pericentric or paracentric) does NOT proceed through meiosis?
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Paracentric because the centromere is not involved.
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A child presents with microcephaly, severe mental retardation, high-pitched-crying, epicanthal folds, and cardiac abnormalities. What is the disease and what is the genetic cause?
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Cri du chat, deletion of the short arm of chromosome 5
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What are the abnormalities noted in 22q11 deletion syndrome?
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CATCH: Cleft palate, abnormal facies, thymic aplasia/T-cell deficiency, cardiac defects, hypOcalcemia from parathyroid aplasia
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What is the difference between DiGeorge syndrome and velocardiofacial syndrome?
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DiGeorge: thymic, parathyroid and cardiac defects; velocardiofacial syndrome: palate, facial, and cardiac defects. Both a part of 22q11 deletion syndromes.
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What branchial pouches are associated with DiGeorge syndrome (22q11 deletion syndrome)?
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The 3rd and 4th pouches
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Full term neonate of an uneventful delivery becomes mentally retarded and hyperactive and has a musty odor. What is the diagnosis?
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PKU
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Stressed executive comes home from work, consumes 7/8 martinis in rapid succession before dinner, and becomes hypoglycemic. What is the mechanism?
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NADH increase prevents gluconeogenesis by shunting pyruvate and oxaloacetate to lactate and malate.
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2 yr old girl has an increase in abdominal girth, failure to thrive, and skin and hair depigmentation. What is the diagnosis?
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Kwashiorkor
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Alcoholic develops a rash, diarrhea and altered mental status. What is the vitamin deficiency?
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Vit B3 (pellagra)
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52-yo man has black spots in his sclera and has noted that his urine turns black upon standing. What is the diagnosis?
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Alkaptonuria
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25 yo man complains of severe chest pain and has xanthomas of his Achilles tendons. What is the disease and where is the defect?
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Familial Hypercholesterolemia; LDL receptor
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Woman complains of intense muscle cramps and darkened urine after exercise. What is the diagnosis?
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McArdle's Diease
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2 parents with albinism have a son who is normal. What genetic mechanism could explain why the son is not affected?
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Locus heterogeneity
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40 yo man has chronic pancreatitis with pancreatic insufficiency. What vitamins are likely deficient?
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Vit. K, A, D, E
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Child exhibits weakness and enlarged calves. What is the disease and how is it inherited?
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Duchenne's muscular dystrophy. X-linked recessive
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Name the fat soluble vitamins.
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Vit K, A, D, E
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Name the water soluble vitamins.
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Vit C, B, Biotin, folate (blood/neural development)
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What is the role of each fat soluble vitamin? Ie vitamin A is involved vision.
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Vit A-vision, Vit D-bone calcification, Calcium homeostasis, Vit K-clotting factors, Vit E-antioxidant
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Name the B vitamins.
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Metabolic: Vit B1-Thiamine (TPP), Vit B2-Riboflavin (FAD, FMN), Vit B3-niacin (NAD+), Vit B5-pantothenic acid (CoA), Vit B6-pyridoxine (PLP), Vit B12-cobalamin (blood, CNS)
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Absorption of fat soluble vitamins are dependent on what organ(s)?
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Pancreas and gut (ileum)
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Name some malabsorptive disorders that can affect fat soluble vitamins?
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cystic fibrosis, sprue, or mineral oil intake
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Name the symptoms in B-complex deficiences.
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dermatitis, glossitis, and diarrhea
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What are the symptoms of vit A deficiency?
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night blindness, dry skin
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What are the symptoms of Vit A excess?
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arthralgias, fatigue, headaches, skin changes, sore throat, alopecia
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What is Vit A function and what is its food type.
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Vit A is constituent of visual pigments (retinal) and is found in leafy vegetables.
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What are the symptoms of Vit B1 deficiency?
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beriberi and Wernicke-Korsakoff syndrome . Seen in alcoholism and malnutrition. Mnemonic: spell beriberia as Ber1Ber1
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What is the function of Vit B1?
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In thiamine pyrophosphate, a cofactor for oxidative decarboxylation of alpha-ketoacids (pyruvate, alpha-ketoglutarate) and branched-chain AA dehydrogenase, and a cofactor for transketolase in the HMP shunt.
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Name the two types of beriberi and their symptoms.
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Dry beriberi: polyneuritis, symmetrical muscle wasting; Wet Beriber: high output cardiac failure (dilated cardiomyopathy), edema
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What are the symptoms of Vit B2 (riboflavin) deficiency?
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angular stomatitis (inflammation of oral mucous linings), cheilosis (inflammation of lips), corneal vascularization; mnemonic=2C's
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What is Vit B2 function?
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cofactor in oxidation and reduction ie FADH2; FAD and FMN are derived from riboFlavin (B2=2ATP)
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What amino acid is Vit B3(niacin) made from?
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Niacin is made by the body from tryptophan. Synthesis requires B6.
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What are the symptoms of Pellagra?
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3 D's: diarrhea, dementia, dermatitis (also beefy glossitis)
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What are some of the causes of Pellagra?
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Pellagra can be caused by Hartnup disease (decreased tryptophan absorption), malignant carcinoid syndrome (increased tryptophan metabolism) and INH (decreased from Vit B6)
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What is the function of Vit B3 (niacin)?
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Vit B3 is a constituent of NAD+/NADP+ (used in redox reactions). Derived from tryptophan using Vit B6.
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What are the symptoms of vit B5 (pantothenate) deficiency?
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Dermatitis, enteritis, alopecia, adrenal insufficieny
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What is the function of Vit B5?
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Vit B5 is a constituent of CoA (a cofactor for acyl transfers) and component of fatty acid synthase. Mnemonic: Pantothen-A is in Co-A
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What are the symtoms of Vit B 6 (pyridoxine )deficiency?
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convulsions, hyperirritability (deficiency include by INH and OCP), peripheral neuropathy.
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What is the function of Vit B6?
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Vit. B 6 is converted to pyridoxal phosphate, a cofactor used in transamination (ie ALT and AST), decarboxylation reactions, glycogen phosphorylase, and heme synthesis. Required for the synthesis of niacin from tryptophan.
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What are the symptoms of Vit B12 (cobalamin) deficiency?
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Macrocytic, megablastic anemia, neurologic symptoms (optic neuropathy, subacute combined degeneration, paresthesia), glossitis
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What food products is vit B12 found in?
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Animal products
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What is the function of Vit B12?
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cofactor for homocysteine methyltransferase (transfers methyl groups as methylcobalamin) and methylmalonyl-CoA mutase.
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Where is Vit B12 stored and for how long?
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Liver, very large reserve pool (several years)
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What are some of the causes of Vit b12 deficiency?
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malabsorption-sprue, diphyllobothrium latum, lack of intrinsic factor (pernicious anemia, gastric bypass surgery) or absence of terminal ileum (Crohn's disease)
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What is the test used to differentiate the etiology of Vit B12 deficiency?
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Schilling test
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What is the cause of neurologic symptoms in Vit B12 deficieny?
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abnormal myelin seen in B12 deficiency; possibly due to decreased methionine or increased methylmalonic acid (from metabolism of accumulated methylmalonyl-CoA)
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What is the most common vitamin deficiency in the US?
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Folate acid
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What are the symptoms of folic acid deficiency and what is the vitamin food source?
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Symptoms: macrocytic, megablastic anemia (often no neurologic symptoms as compared to Vit B12 deficiency); Folate acid can be obtained from green leaves (b/c folic acid is not stored very long). Supplemental folic acid in early pregnancy can reduce neural tube defects. Mnemonic: FOLate from FOLiage
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What is the function of folic acid?
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Coenzyme (THF) for 1-carbon transfer; involved in methylation reactions. Important for the synthesis of nitrogenous bases in DNA and RNA
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What are the symptoms of biotin deficiency?
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dermatitis, enteritis.
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What are the causes of biotin deficiency?
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antibiotic use and excessive ingestion of raw eggs. Mnemonic: AVIDin in egg whites AVIDly binds biotin
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What is the function of biotin?
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Cofactor for carboxylations: 1) pyruvate to oxaloacetate 2) Acetyl-CoA to malonyl-CoA 3) Propionyl-CoA to methylmalonyl-CoA
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What are the symptoms of Vit C deficiency?
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scurvy-swollen gums, bruising, anemia, poor wound healing
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What is the function of Vit C?
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necessary for hydroxylation of proline and lysine in collagen synthesis. Facilitates iron absorption by keeping iron in Fe2+ reduced state (more absorbable). Necessary as a cofactor for dopamine beta-hydroxylase, which converts dopamine to NE
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What are the sources of Vit D2 and D3?
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D2=ergocalciferol consumed in milk; D3=cholecalciferol, formed in sun-exposed skin
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What is the storage form and active form of Vit D?
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25-OH D3=storage form; 1,25 (OH)2 D3=active form, aka calcitriol
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What are the symptoms of Vit D deficiency?
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Rickets in children (bending bones), osteomalacia in adult (soft bones) and hypocalcemic tetany
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What is the function of Vit D?
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Increased intestinal absorption of calcium and phosphate
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What are the symptoms of excess Vit D?
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hypercalcemia, loss of appetite, stupor. Seen in sarcoidosis, a disease where the epitheloid macrophages convert vit D into its active form.
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What are the symptoms of Vit E deficiency?
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increased fragility of erythrocytes, neurodysfunction Mnemonic: Vitamin E for Erythrocytes
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What is the function of Vit E?
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antioxidant (protects RBCs from hemolysis)
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What are the symptoms of Vit K deficiency?
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neonatal hemorrhage with increased PT and aPTT but normal bleeding time, b/c neonates have sterile intestines and are unable to synthesize vit K. Mnemonic: K for Koagulation. Note: neonates are given Vit K injection at birth to prevent hemorrhage.
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What are the vit K-dependent clotting factors?
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factors 2, 7, 9, 10 and protein C and S.
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What drug is a vitamin K antagonist?
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warfarin
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What is the function of Vit K?
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catalyzes gamma-carboxylation of glutamic acid residues on various proteins concerned with blood clotting. Synthesized by intesting flora. Therefore, vit K deficiency can occur after prolonged use of broad-spectrum antibiotics.
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What are the symptoms of zinc deficiency?
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delayed wound healing, hypogonadism, decrease adult hair (axillary, facial, pubic), may predispose to alcoholic cirrhosis
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What enzyme metabolizes ethanol to acetaldehyde?
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alcohol dehydrogenase
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What enzyme metabolizes acetaldehyde to acetate?
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acetaldehyde dehydrogenase
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What drug inhibits alcohol dehydrogenase?
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fomepizole
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What drug inhibits acetaldehyde dehydrogenase?
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disulfiram (antabuse), result in accumulation of acetaldehyde contributing to hangover symptoms
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What is the limiting reagent in ethanol metabolism?
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NAD+
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What is the kinetics of alcohol dehydrogenase?
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zero-order
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What is the pathophysiological mechanism of ethanol hypoglycemia?
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Ethanol metabolism increases NADH/NAD+ ratio in liver, causing diversion of pyruvate to lactate and OAA to malate, thereby inhibiting gluconeogenesis and leading to hypoglycemia. This altered NADH/NAD+ ratio is responsible for the hepatic fatty change (hepatocellular steatosis) seen in chronic alcoholics (shunting away from glycolysis and toward fatty acid synthesis, which normalizes the ratio).
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What is the pathology behind Kwashiorkor?
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protein malnutrition
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What are the symptoms of Kwashiorkor?
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skin lesions, edema, liver malfunction (fatty change). Clinical picture is a small child with swollen belly. Mnemonic: Kwashiorkor results form protein deficient MEAL: Malnutrition, Edema, Anemia, Liver (fatty)
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What is the pathology behind Marasmus?
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energy malnutrition (low calorie intake)
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What are the symptoms of Marasmus?
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tissue and muscle wasting, loss of subcutaneous fat and variable edema
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