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Biochemistry Post Midterm > Inherited Disorders > Flashcards

Inherited Disorders Flashcards

1
Q

what is the most common fatal autosomal recessive disorder in Caucaisna children (1:2000)?

A

CF

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2
Q

what causes CF?

A

mutation in the gene for ‘cystic fibrosis transmembrane conductance regulator’ (CFTR

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3
Q

what is CFTR?

A

membrane protein that acts as a cholride channel

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4
Q

what type of transporter is CFTR?

A

ATP binding cassette (ABC) transporter

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5
Q

what does CFTR contain

A
  • 2 membrane spanning domains
  • 2 ATP binding domains
  • regulatory domain that can be phosphorylated by PKA
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6
Q

what does phosphorylation of the cytoplasmic regulatory domain by PKA activate?

A

the channel - providing regulated Cl- and fluid secretion

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7
Q

what are the changes in the respiratory system with CF?

A

the mutant CFTR does not transport Cl- into the airway lumen!

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8
Q

what does mutant CFTR in respiratory system lead to?

A

-Na+ and H20 in luminal surface is low
= thickened and viscous mucous secretions
leads to bacterial infections!

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9
Q

what are the most common causes of mortality and morbidity in patients with CF?

A

respiratory infections

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10
Q

what major change in the pancreas is found with CF?

A

exocrine pancreatic insufficiency

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11
Q

a loss of CFTR function leads to thicker acinar secretions which leads to?

A

duct obstruction and tissue destruction

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12
Q

what types of tissues replace the pancreatic parenchyma?

A

fibrotic tissue and fat - “CF”

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13
Q

is there a defiency of pancreatic enzymes in CF?

A

yes - lipase, trypsin, chymotrypsin

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14
Q

why is there steatorrhea with CF/

A

defieincy of fat soluble vitamins

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15
Q

what is commonly found in some children right after birth with CF?

A

meconium ileus and intestinal obstruction

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16
Q

more than 95% of males with CF are what?

A

infertile

because they lack a vas deferens - a phenotype known as CONGENITAL BILATERAL ABSENCE OF TEH VAS DEFERENS (CBAVD)

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17
Q

what is CFTR function in sweat glands?

A

reabsorption of NaCl - defective in CF - high salt content in skin!

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18
Q

the presence of what is diagnostic of CF?

A

excessive salt in sweat

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19
Q

where is the CFTR mutation located?

A

long arm of chromosome 7

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20
Q

what is the most common mutation of CFTR?

A

A F508
deletion of 1 aa = 3 bp deletion that eliminates the phenlylalanine residue of CFTR at position 508

NBD1 - defective processing!

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21
Q

what does the F508 mutation prevent?

A

protein from maturing properly and reaching the plasma membrane

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22
Q

what is pilocarpine?

A

a drug that stimulates sweating

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23
Q

what are some molecular diagnostic tests to diagnose CF?

A

ASO - if mutation is known
PCR
Southern blot
Allel specific PCR

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24
Q

the carriers for CF are _____ wheras the affected children are ____ for the mutation?

A

heterozygous

homozygous

25
Q

what sickle cell due to?

A

point mutation of the beta globin chain of Hb

26
Q

what is replaced in sickle cell anemia?

A

glutamic acid (glutamate) is replaced with valine at the 6th position of the beta glob in chain of Hb

27
Q

the acidic aa that was ____ is replaced with a _____ aa?

A 
hydrophilic
branches chain (hydrophobic)
28
Q

where is glutamate normally present?

A

exterior of the Hb molecule

29
Q

what does the replacement of valine in sickle cell disease result in?

A

creation of a hydrophobic pocket on the exterior of the Hb molecule

30
Q

what happens to Hb in sickle cell in deoxygenated state

A

Hb aggregates to form long filament like structures - results in distortion of the structure of RBC = sickling!

31
Q

when is HbS less soluble?

A

in deox state - this is why sickling is seen more in periphery - deox Hb levels are higher in limbs

32
Q

a single aa change in Hb is what?

A

critical for solubility of Hb

33
Q

how are sickled and distorted RBC removed ?

A

spleen - this is why they have anemia/splenomegaly

34
Q

how can sickling crisis result?

A

excessive removal of sickled RBCs from the circulation - resulting in worse anemia and jaundice (hyperbilirubinemia) during the crisis

35
Q

what type is hyperbilirubinemia in sickle cell?

A

pre-heptic (hemolytic type)

36
Q

what is hyperbilirubinemia in sickle cell characterized by?

A

increase unconjugated (indirect) bilirubin - bound to albumin
increase in total bilirubin
urine is normal color

37
Q

why may people with sickle cell anemia develop pigmented gall stones?

A

due to excessive loss of conjugated bilirubin in bile

38
Q

HbS has fewer _____- than HbA

A

number of negative charges - HbS moves slower than HbA towards the anode (+)

39
Q

what are molecular diagnostic tests for detection of sickle cell disease and carriers?

A

ASO test - dot blot test

RFLP analysis

40
Q

DMD and BMD are mutations of what?

A

dystrophin gene

41
Q

the dystrophin gene is the largest gene located on what chromosome?

A

X

42
Q

what id DMD due to?

A

almost complete absence of functional dystrophin

43
Q

what is BMD due to ?

A

production of abnormal dystrophin or less amounts of dystrophin

44
Q

what does DMD prevent the production of?

A

dystrophin - muscle protein

45
Q

what is the most common MD resulting in 1:3,000 boys?

A

DMD

46
Q

which MD is more severe?

A

DMD - severe with early onset!

BMD is milder - with later onset

47
Q

on what level can DMD and BMD deletions be distinguished from eachtoehr?

A

codon level

48
Q

almost all deletions causing DMD involve what?

A

frameshift mutations

abolishing translation of dystrophin protein

49
Q

BMD deletions are mostly?

A 
in frame
some dystrophin (although truncated) is translated!
50
Q

what tool is needed to diagnose DMD?

A

multiplex PCR

51
Q

what are the clinical features of DMD?

A

weakness in muscles - pecs, trunk, upper and lower legs

pseudohypertrophy of calf - due to replacement of normal muscle with CT and fat

52
Q

what is Gower’s maneuver?

A

DMD boys distinct way of getting up from floor

53
Q

what is the function of dystrophin?

A

anchors the cytoskeleton of msucle cells to the ECM

links actin filaments to TMP of the muscle cell plasma memrbane

54
Q

what does the dystrophin anchor do?

A

stabilize the PM and enables the cell to withdtand the stress of muscle contraction

55
Q

function loss of dystrphin leads to what?

A

ocidative cellular injury and myonecrosis

56
Q

what can immunofluorescence staining indicate with Md?

A

increase in CT between myocytes

57
Q

what is western blot used for in MD?

A

can show protein size and quantity of protein - BMD = in frame
DMD = complete absence - frame shift deletion

58
Q

what are other useful tests used in DMD?

A

CKMM - elevated with MD (indicated muscle damage)
females are carriers - have higher CKMM
multiplex PCR is used to Id specific mutation

Biochemistry Post Midterm (24 decks)

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