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USMLE me > biochem and genetics incorrects > Flashcards

biochem and genetics incorrects Flashcards

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USMLE® Step 1 flashcards
1
Q

if DNA needs to be TRANSCRIBED, what method are you using?

A

Northern blot

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2
Q

mutations that result in loss of 2-3BPG cause hemoglobin to resemble what?

A

Fetal hemoglobin (binds with high affinity)

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3
Q

metabolism 1g of protein, carbs and fat each produces how much energy?

A

protein and carbs = 4 cal each
fat = 9 cal

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4
Q

alkapTonuria (black urine, arthritis) results from failed conversion of?

A

Tyrosine to fumarate. Homgencitic oxidase dysfucntional. HGA builds up

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5
Q

how is UV light damage repaired?

A

Nicking of the damaged strand on both sides of pyridimine dimer

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6
Q

Lesch Nyan syndrome (lip biting (self mutilation) dystonia, uric acid in urine) results in buildup of what molecule?

A

PRPP

(HGPRT activity reduced)

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7
Q

why is repeated deoxythymidine residues likely to bind to mature MRNA?

A

due to presence of polyAtail

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8
Q

a 17 year old girl with fatal aortic dissection and ovaries composed of connective tissue is also likely to have what?

A

renal fusion (turners syndrome)

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9
Q

vomiting from brestfeeds, cardiomegaly, hepatomegaly and decreased erythrocyte transketolase activity in an infant may all point to?

A

thiamine deficiency (beri beri)
- defective pyruvate dehydrogenase activity

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10
Q

karyotype/ chromosomes for a complete mole?

partial mole?

A

complete = empty ovum fetilised and duplication of sperm DNA = 46XX most common

Partial mole has fetal parts and = 69XXX for example. It is 2 sperm and 1 egg

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11
Q

pyruvate conversion into glucose is first prompted by what enzyme?

A

acetyl coa
also inhibits glycolysis via inhibiting pyrivate dehydrogenase

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12
Q

insulin acts on tyrosine kinase to promote protein synthesis via activity on which enzyme?

A

protein phosphatase (it activates glycogen synthase)

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13
Q

decreased activity of what enzyme can be linked to cholesterol stone formation?

A

cholesterol-7 alpha hydroxylase (fibrate medications eg fenofibrate gemfibrozil inhibit this and favour cholesterol stone formation)

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14
Q

which cell in body can carry out glycoslysis and yield pyruvate but no net ATP?

A

erythrocytes

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15
Q

which sybstance is metabolised fastest in glycolytic pathway and why?

A

fructose 1 phosphate -> bypasses PFK-1

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16
Q

ehlers danlos syndrome is due to abnormal what?

A

collagen

  • impaired n terminal propeptide removal in collagen (procollagen peptidase deficiency)

condition causes easy bruising and hyperextendible skin

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17
Q

PTH effects on 1,25 vitamin D levels

A

increases

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18
Q

increased PRPP activity most likely causes?

NSAIDS used for treatment inhibit which cell line?

A

joint disease -gout - due to increased production and degradation of purines

neutrophils

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19
Q

DNA polymerase 3 vs polymerase 1 activity

A

check phone/book

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20
Q

Key signs of HCM include left sternal sided murmur and dyspnea. what is the mode of inheritance for this?

A

Autosomal dominant

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21
Q

Hartnups disease which causes ataxia and neutral amino acids in urine can be treated with which vitamin?

A

niacin

22
Q

role of PFK enzymes and fructose-2,6-BP?

A

increase glycolysis
Prince frederick only works when fed.

There for gluconeogenesis will be inhibited, inhibiting things like alanine -> glucose

23
Q

flat facial profile, protruding tongue and small ears are features of what condition

A

down syndrome

24
Q

do hemoglobin molecules release h+ or Cl- as they become saturated?

A

H+

25
Q

Sorbitol is typically metabolised to ?

A

fructose
- review this pathway

26
Q

integrin binds to what in the ECM?

A

fibronectin!!!
collagen
laminin

27
Q

cortisol effect on epinephrine synthesis?

A

decreases conversion of norepineprine to epinephrine via inhibition of

PHENYLETHANOLAMINE -N -METHYLTRANSFERASE (PNMT)

28
Q

KRAS is active when bound to which molecule?

A

GTP

29
Q

tay sachs disease results in accumulation of?

A

GM2 ganglioside

30
Q

sideroblastic anemia is caused by defects in ezyme that catalyses what?

A

glycine + succinyl coA joining

31
Q

large anterior fontanelle, umbilical hernia, macroglossia in the presence of a floppy baby (hypotonia) is concerning for what?

A

congenital hypothyroidism

32
Q

imparied transport of ornithine can be treated by?

A

protein restriction

33
Q

hardy weinberg calculation example

A
34
Q

renal cell carcinoma is due to mutation of which gene?

A

VHL

35
Q

methylation of MGMT reduces tumour cells ability to?

A

repair DNA damage

36
Q

how does CO bind to Heme

A

REVERSIBLY! (NON-COMPETITIVE0

37
Q

glycerol kinase is used in ?

A

gluconeogenesis

38
Q

in essential fructokinase, patients are able to metabolise glucose through the compensatory action of?

A

hexokinase

39
Q

which hormones are DNA binding?

A

steroid receptors - cortisol aldosterone progesterone

fat soulble vitmain receptors - Vitamin D

40
Q

the greenish colour of wounds is caused by?

A

heme oxygenase -> converts heme to biliverdin

41
Q

oxaloaceteate to phsphoneylpyruvate is a reaction seen in?

A

gluconeogenesis

42
Q

matuity onset diabetes of the young is due to mutations in?

A

Glucokinase - modulates pancreatic beta cell function

43
Q

RNA made of bases dihydrouridine, pseudouridine, ribothymidine is most likely to have what at its -3 end?

A

CCA
reference is to TRNA
CCA tail is amino acid binding site

44
Q

why are SNRAs involved in removal of introns from RNA transcripts?

A

form spliceosome

45
Q

homocystinuria (ectopic lens, marfanoid body habitus) can be treated with?

A

pyridoxine

46
Q

heme synthesis cant occur in erythrocytes due to lack of?

A

mitochondria

47
Q

acidosis causes renal metabolism of what amino acid? to maintain acid excetion

A

glutamine

48
Q

virilization and male-pattern baldness can occur as a result of a mutation in which cellular organelle?

A

smooth ER
(synthesises steroids/sex steroids)

49
Q

mushroom toxins inhibit rna polymerase 2 and therefore halt synthesis of?

A

MRNA

50
Q

rate of glycogenolysis increases during skeletal muscle contraction due to presence of?

A

calcium

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