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USMLE Step I > Biochem > Flashcards

Biochem Flashcards

1
Q

Interfere with nucleotide synthesis: Leflunomide

A

qinhibits dihydroorotate dehydrogenase

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2
Q

Interfere with nucleotide synthesis:Mycophenolate and ribavirin

A

inhibit IMP dehydrogenase

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3
Q

Interfere with nucleotide synthesis:Hydroxyurea

A

inhibits ribonucleotide reductase

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4
Q

Interfere with nucleotide synthesis:6-Mercaptopurin(and prodrug azathioprine

A

inhibit de novo purine synthesis

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5
Q

Interfere with nucleotide synthesis:5-FU

A

inhibit thymidyalte synthase (decreases dTMP)

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6
Q

Interfere with nucleotide synthesis:Methotrexate, thrimethoprim, and pyrimethamine

A

inhibit dihydrofolate reductase in humans, bacteria, and protozoa

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7
Q

abnormal splicing variant disease example

A

beta-thalassemia

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8
Q

t-arm of tRNA

A

thymine psuedouridine cytosine

necessary for ribosome binding

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9
Q

d- arm of t RNA

A

dihydrouracil

recognition by aminoacyle trNA synthase

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10
Q

variable phase of cell cycle

A

G1 and G0

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11
Q

shortest phase of cell cycle

A

mitosis

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12
Q

Li Fraumeni syndrome

A

mutations in p53 and Rb =unrestrained cell division

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13
Q

N-linked oligosaccarhide addition

A

occurs in RER

adds to ASPARAGINE

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14
Q

O-linked oligosaccarhide addition

A

occurs in GA

adds to serine and threonine

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15
Q

I cell disease

A

inherited lysosomal storage disorder
GA fails to phophorylate mannose residues on glycoproteins
proteins excreted extracellularly
coarse facial features, clouded corneas, stiff joints, high plasma levels of lysosomal proteins
fatal in childhood

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16
Q

Drugs that act on microtubules

A

Mebendazole (anti-helminthic)
Griseofulvin (anti-fungal)
Colchicine (anti gout)
Vincristine and Vinblastine (anti cancer)
Paclitaxel (anti cancer)
(Microtubules Get Constructed Very Poorly)

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17
Q

cilia structure

A

9+2 arrangement of microtubules with axonemal dynein ATPase links

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18
Q

Kartagener syndrome (primary ciliary dyskinesia)

A

immotile cilia due to dynein arm defect
male and female infertility (sperm, fallopian tube)
increased risk of ectopic pregnancy, bronchiectasis, recurrent sinusitis etc

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19
Q

Ouabain

A

inhibits Na/K ATPase by binding to K site

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20
Q

digoxin and digitoxin

A

directly inhibit Na/K ATPase = indirect inhibition of Na/Ca exchange = increased intracellular Ca = increased cardiac contractility

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21
Q

Type three collagen defects

A

vascular type of Ehlers-Danlos

defect in cross linking of collagen;in osteogenesis imperfect T1 collagen and can’t form collagen triple helix

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22
Q

Type four collagen defects

A

Alport syndrome

targeted by autoantibodies in Goodpasture

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23
Q

Copper is a necessary cofactor for…

A
  • lysyl oxidase

- deficiency in copper = kinky hair, growth retardation, and hypotonia

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24
Q

alpha antitrypsin deficiency

A

emphysema; due to excess elastase activity

25
Q

confirmatory test for HIV

A

Western blot; after ELISA

26
Q

codominance examples

A

A,B, O and alpha anti-trypsin

27
Q

variable expressivity

A

variable phenotype with same genotype; NF1

28
Q

incomplete penetrance

A

BRCA

29
Q

pleiotropy

A

one gene produces multiple unrelated phenotypic effects; PKU = mental retardation, light skin, and musty odor

30
Q

dominant negative mutation

A

nonfunctional protein produced from the mutant gene prevent the the normal protein product from working

31
Q

locus heterogeneity

A

different loci produce the same phenotype; albinism

32
Q

allelic heterogeneity

A

different mutation at the same locus produce the same phenotype; beta-thal

33
Q

carrier frequency (autosomal recessive)

A

2pq

34
Q

x linked recessive frequency males

A

q

35
Q

x linked recessive frequency females

A

q^2

36
Q

chromosome 15

A

Prader-Willi and angelman; both can also be caused by uniparental disomy instead of imprinting

37
Q

Prader-Willi syndrome

A

maternal gene is noramlly silent and the paternal gene gets deleted
-hypogonadism, hypotonia, obesity, and hyperphagia

38
Q

Angelman

A

paternal gene is normally silent and the maternal gene gets deleted
-inappropriate laughter and seizures

39
Q

x-linked dominant example

A

hypophosphatemic rickets; affected father will always transmit to daughter and never transmit to son; affected mother can transmit to daughter or son at 50% risk

40
Q

mitochondrial inheritance

A

mitochondrial myopathies= ragged red fiber, lactic acidosis and CNS disease

41
Q

polycystic kidney disease

A

autosomal dominant, chrom 16, PKD1

always bilaters, massive enlargement due to multiple large cysts

42
Q

familial adenomatous polyposis

A

autosomal D, chrom 5 , APC

progress to cancer unless resected

43
Q

familial hypercholesterolemia

A

AD
absent LDL receptor
endon xanthomas

44
Q

hereditary hemorrhagic telangiectasia

A

AD

telangiectasia, recurrent epistaxis, skin discolorations, GI bleeds, hematuria

45
Q

hereditary sphereocytosis

A

AD
elevated MCHC
treatmetn splenectomy

46
Q

Huntingtons

A

AD, chrom 4, CAG repeat disorder
caudate atrophy
decreased GABA and ACh in the brain

47
Q

Marfan

A

AD,

pectus excavatum, hypermobile joints, long fingers, floppy mitral valve , subluxation of lenses

48
Q

multiple endocrine neoplasias

A

AD, Men2A and B = ret gene

tumor of multiple different endocrine genes

49
Q

Neurofibromatosis T1

A

AD, chrom 17, NF1
100% penetrance with variable expression
cafe au lait and cutaneous neurofibromas

50
Q

Neurofibromatosis T2

A

AD, chrom22, Nf2

bilateral acoustic schwannomas, juvenile cataracts, memingiomas, and ependymomas

51
Q

tuberous sclerosis

A

AD, incomplete penetrance, with variable expression
neurocutaneous disorder with multi organ system involvement
characterized by numerous benign hamartomas

52
Q

von Hippel-Lindau

A

AD, chrom 3, deletion of VHL gene (tumor supressor gene)

numerous tumors both begin and malignant

53
Q

cystic fibrosis

A

AR, defect CFTR, chrom 7 , commonly deletion of 508

54
Q

x linked recessive disorders

A

Be Wise, Fools GOLD Heeds Sily H0pe
brutons agam, wiskott-ald, fabrys, G6PD, ocular albinism, Lesch-Nyhan, Duchhens and Beckes, Hunters , Hemophil A and B, and ornithine transcarbamylase

55
Q

myotonic type 1 muscular dystrophy

A

CTG trinucleotide repeat expansion in the DMPK gene
myotonia, , muscle wasting, frontal balding, catarats, testicular atrophy, arrythmias
***think of the D in DMPK as degenerative = symptoms associated with old age

56
Q

Trinucleotide repeat expansions

A

Huntingtons = CAG
Fragile X= CGG
Myotonic dystrophy= CTG
Friedrich axtaxia = GAA

57
Q

Robertsonian translocation

A

commonly involves 13,114,15,21,22

58
Q

Cri du chat

A

congential micro deletion of chromosome 5 (46XX/XY 5p-)

high pithed cry, microcephaly, intellectual disability, and epidcanthal folds, cardiac abnormalities

59
Q

Williams syndrome

A

congential micro deletion of long arm of jchromosome 7 (deleted region inculdes elastin gene)
distinctive elfin facies, extreme friendliness with strangers, well developed verbal skills, intellectual disability, cardiovascular problems, hypercalcemia

USMLE Step I (2 decks)

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