USMLE Biochemistry & Genetics

reynch02's version from 2015-06-01 14:00

Metabolic Syndromes

Question Answer
Orotic aciduria defectUMP synthase
Orotic aciduria inheritanceAutosomal recessive
Orotic aciduria upstreamOrotic acid
Orotic aciduria downstreamUMP (de novo pyrimidine synthesis)
Adenosine deaminase deficiency pathwayPurine salvage pathway
Adenosine deaminase upstreamATP & dATP
Lesch-Nyhan syndrome defectHGPRT
Lesch-Nyhan syndrome inheritanceX-linked recessive
Lesch-Nyhan syndrome upstreamGuanine, hypoxanthine, xanthine, *uric acid
Lesch-Nyhan syndrome downstreamGMP, IMP
I-cell (inclusion cell) disease defectPhosphotransferase
Metachromatic leukodystrophy inheritanceAutosomal recessive
Metachromatic leukodystrophy defectArylsulfatase A deficiency
Krabbe disease defectGalactocerebrosidase deficiency
Maturity-onset diabetes of young (MODY) defectGlucokinase
Essential fructosuria defectFructokinase
Fructose intolerance defectAldolase B deficiency
Fructose intolerance upstreamFructose-1-P
Galactokinase deficiency upstreamGalactitol (from buildup of galactose)
Classic galactosemia defectGalactose-1-phosphate uridyltransferase
Classic galactosemia upstreamGalactitol (from buildup of galactose)
Alkaptonuria defectHomogentisate oxidase deficiency
Alkaptonuria downstreamFumarate
Maple syrup urine disease defecta-Ketoacid dehydrogenase
Maple syrup urine disease upstreamBranched amino acids
Von Gierke (type I) defectGlucose-6-phosphatase
Pompe (type II) defectLysosomal a-1,4-glucosidase (acid maltase)
Cori (type III) defectDebranching enzyme (a-1,6-glucosidase)
McArdle (type V) defectSkeletal muscle glycogen phosphorylase
Fabry disease defecta-Galactosidase A
Fabry disease upstreamCeramide trihexoside
Gaucher disease defectGlucocerebrosidase (b-glucosidase)
Gaucher disease upstreamGlucocerebroside
Niemann-Pick disease defectSphingomyelinase
Niemann-Pick disease upstreamSphingomyelin
Tay-Sachs disease defectHexosaminidase A
Tay-Sachs disease upstreamGM2 ganglioside
Krabbe disease defectGalactocerebrosidase
Krabbe disease upstreamGalactocerebroside, psychosine
Metachromatic leukodystrophy defectArylsulfatase A
Metachromatic leukodystrophy upstreamCerebroside sulfate
Hurler Syndrome defecta-L-iduronidase
Hurler syndrome upstreamHeparan sulfate, Dermatan sulfate
Hunter syndrome defectIduronate sulfatase
Hunter syndrome upstreamHeparan sulfate, Dermatan sulfate
Hartnup disease defectDeficiency of neutral amino acid (e.g. tryptophan) transporters in proximal tubules & enterocytes

Genetic Syndromes

Question Answer
Xeroderma pigmentosum defectNucleotide excision repair (pyrimidine dimers)
Hereditary nonpolyposis colorectal cancer (HNPCC) defectDNA mismatch repair
Ataxia telangiectasia defectMutated nonhomologous end joining
Classical type Ehlers-Danlos defectType V collagen mutation
Vascular type Ehlers-Danlos defectType III collagen deficiency
Marfan syndrome defectFibrillin defect

Syndrome Inheritance

Question Answer
Osteogenesis imperfectaAutosomal dominant
Ehlers-Danlos syndromeAutosomal dominant or recessive
Prader-Willi syndromeMaternal uniparental disomy (chr 15)
Angelman syndromePaternal uniparental disomy (chr 15)
Hypophosphatemic ricketsX-linked dominant
Autosomal dominant polycystic kidney disease (ADPKD)Autosomal dominant (chr 16 or 4)
Familial adenomatous polyposisAutosomal dominant (chr 5, APC gene)
Familial hypercholesterolemiaAutosomal dominant
Hereditary hemorrhagic telangiectasiaAutosomal dominant
Hereditary spherocytosisAutosomal dominant
Huntington diseaseAutosomal dominant (chr 4; trinucleotide repeat [CAG])
Marfan SyndromeAutosomal dominant (Fibrillin-1 gene)
Multiple endocrine neoplasias (MEN)Autosomal dominant
Neurofibromatosis type 1 (von Recklinghausen disease)Autosomal dominant (chr 17, NF1 gene)
Neurofibromatosis type 2Autosomal dominant (chr 22, NF2 gene)
Tuberous sclerosisAutosomal dominant
Von Hippel-Lindau diseaseAutosomal dominant (chr 3p, VHL gene deletion)
AlbinismAutosomal recessive
ARPKDAutosomal recessive
Cystic fibrosisAutosomal recessive (chr 7, CFTR gene defect [usually delta-F508])
Glycogen storage diseasesAutosomal recessive
HemochromatosisAutosomal recessive
Kartagener syndromeAutosomal recessive
Mucopolysaccharidoses (minus Hunter syndrome)Autosomal recessive
PhenylketonuriaAutosomal recessive
Sickle cell anemiaAutosomal recessive
Sphingolipidoses (except Fabry disease)Autosomal recessive
ThalassemiasAutosomal recessive
Wilson diseaseAutosomal recessive
Bruton agammaglobulinemiaX-linked recessive
Wiskott-Aldrich syndromeX-linked recessive
Fabry diseaseX-linked recessive
G6PD deficiencyX-linked recessive
Ocular albinismX-linked recessive
Lesch-Nyhan syndromeX-linked recessive
Duchenne (& Becker) muscular dystrophyX-linked recessive (dystrophin gene)
Hunter syndromeX-linked recessive
Hemophilia A & BX-linked recessive
Ornithine transcarbamylase deficiencyX-linked recessive
Fragile X syndromeTrinucleotide repeat disorder (CGG) of FMR1 gene
Friedreich ataxiaTrinucleotide repeat disorder (GAA)
Myotonic dystrophyTrinucleotide repeat disorder (CTG) of DMPK gene
Edwards syndromeTrisomy 18
Patau syndromeTrisomy 13
Cri-du-chat syndrome5p congenital microdeletion
Williams syndrome7q congenital microdeletion
DiGeorge syndrome22q11 deletion
Velocardiofacial syndrome22q11 deletion
Charcot-Marie-Tooth diseaseAutosomal dominant (typically)
Krabbe diseaseAutosomal recessive
Essential fructosuriaAutosomal recessive
Fructose intoleranceAutosomal recessive
Galactokinase deficiencyAutosomal recessive
Classic galactosemiaAutosomal recessive
AlkaptonuriaAutosomal recessive
HomocystinuriaAutosomal recessive
CystinuriaAutosomal recessive
Maple syrup urine diseaseAutosomal recessive
Hyper-chylomicronemia (type I dyslipidemia)Autosomal recessive
Familial hyper-cholesterolemia (type IIa dyslipidemia)Autosomal dominant
Hyper-triglyceridemia (type IV dyslipidemia)Autosomal dominant
IL-12 receptor deficiencyAutosomal recessive
Job (hyper-IgE) syndromeAutosomal dominant
SCID – IL-2R gamma chain defectX-linked
SCID – adenosine deaminase deficiencyAutosomal recessive
Ataxia telangiectasiaAutosomal recessive
Hyper-IgM syndromeX-linked recessive
Leukocyte adhesion deficiency (type I)Autosomal recessive
Chediak-Higashi syndromeAutosomal recessive
Chronic granulomatous diseaseX-linked recessive
Hartnup diseaseAutosomal recessive
Gitelman syndromeAutosomal recessive
Bartter syndromeAutosomal recessive
Liddle syndromeAutosomal dominant
Werdnig-Hoffman disease (floppy baby)Autosomal recessive

Water Soluble Vitamin Common Names

Question Answer
B1Thiamine (TPP)
B2Riboflavin (FAD, FMN)
B3Niacin (NAD+)
B5Panthothenic acid (CoA)
B6Pyridoxine (PLP)
B9Folate (stored in liver)
B12Cobalamin (stored in liver)
CAscorbic acid

Vitamin Cofactors & Deficiencies

Question Answer
B1 cofactorPyruvate dehydrogenase (link glycolysis to TCA cycle)
B1 cofactora-Ketoglutarate dehydrogenase (TCA cycle)
B1 cofactorTransketolase (HMP shunt)
B1 cofactorBranched-chain ketoacid dehydrogenase
B1 deficiencyWernicke-Korsakoff syndrome, dry & wet beriberi
B3 building blockTryptophan
B3 severe deficiencyPellagra
B6 cofactorTransamination, decarboxylation, glycogen phosphorylase
B7 cofactorCarboxylase enzymes (pyruvate, acetyl-CoA, propionyl-CoA)
B9 absorption siteJejunum

Neurologic Genetic Associations

Question Answer
APP (chr 21)Early onset Alzheimer
Presenilin-1 (chr 14)Early onset Alzheimer
Presenilin-2 (chr 1)Early onset Alzheimer
ApoE4 (chr 19)Late onset Alzheimer
ApoE2 (chr 19)Protective against Alzheimer
a-Synuclein defectLewy body dementia
GNAQ gene mutationSturge-Weber syndrome

Rate-determining Enzymes

Question Answer
TCA cycleIsocitrate dehydrogenase
GlycogenesisGlycogen synthase
GlycogenolysisGlycogen phosphorylase
HMP shuntG6PD
De novo pyrimidine synthesisCarbamoyl phosphate synthetase II
De novo purine synthesisGlutamine-phosphoribosylpyrophosphate (PRPP) amidotransferase
Urea cycleCarbamoyl phosphate synthetase I
Fatty acid synthesisAcetyl-CoA carboxylase
KetogenesisHMG-CoA synthase
Cholesterol synthesisHMG-CoA reductase
PFK-1 (+)AMP, fructose-2,6-bisphosphate
PFK-1 (-)ATP, citrate
Fructose-1,6-bisphosphatase (+)ATP, acetyl-CoA
Fructose-1,6-bisphosphatase (-)AMP, fructose-2,6-bisphosphate
Isocitrate dehydrogenase (+)ADP
Isocitrate dehydrogenase (-)ATP, NADH
Glycogen synthase (+)Glucose-6-phosphate, insulin, cortisol
Glycogen synthase (-)Epinephrine, glucagon
Glycogen phosphorylase (+)Epinephrine, glucagon, AMP
Glycogen phosphorylase (-)Glucose-6-phosphate, insulin, ATP
PRPP amidotransferase (-)AMP, IMP, GMP
Carbamoyl phosphate synthetase I (+)N-acetylglutamate
Acetyl-CoA carboxylase (+)Insulin, citrate
Acetyl-CoA carboxylase (-)Glucagon, palmitoyl-CoA
Carnitine acyltransferase I (-)Malonyl-CoA
HMG-CoA reductase (+)Insulin, thyroxine
HMG-CoA reductase (-)Glucagon, cholesterol


Question Answer
Electron transport inhibitorsRotenone, cyanide, antimycin A, CO
ATP synthase inhibitorsOligomycin