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Boards - Step 1 > First Aid: Biochem/Microbio > Flashcards

First Aid: Biochem/Microbio Flashcards

1
Q

2 syndromes that can be caused by a Robertsonian translocation

A

Downs (trisomy 21) and Patau (trisomy 13)

Robertsonian translocation = when the long arms of 2 acrocentric chromosomes (ones w/ centromere at the ends) fuse and the short arms are lost => chromosomal imbalance

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2
Q

Angelman syndrome

(a) Etiology
(b) Clinical features

A

Angelman syndrome

(a) Gene on chrom 15: paternal allele is imprinted (methylated/turned off), maternal allele is mutated or deleted => disease
(b) ‘Happy puppet’- inappropriate laughter
seizures, ataxia, severe intellectual disability

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3
Q

Differentiate utility of karyotype vs. FISH to detect genetic abnormality

A

Karyotype looks at larger/chromosomal abnormalities, while FISH can look for presence/absence of genes at the molecular level (can look for smaller changes not seen by karyotype)

Karyotype can be done on blood, bone marrow tissue, placenta, amniotic fluid

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4
Q

Differentiate types of DNA mutations: missense, nonsense, frameshift

A
  • missense = substitution that causes change in amino acid in one place of the protein
  • nonsense = substitution that codes for a premature stop codon
  • frameshift totally messes it up = addition or deletion that ruins the 3 divisibility => usually results in truncated/nonfunctional protein
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5
Q

Chromosomal d/o of chrom 7

A

Chrom 7 microdeletion = Williams syndrome: heart defect, ‘elfin’ faces, extreme friendliness w/ strangers

Cystic fibrosis

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6
Q

Explain how alternative splicing increases the number of proteins possible

A

The same exons can be spliced together in different ways (orders) to make a larger variation of proteins from the same genetic code

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7
Q

Differentiate the composition of euk vs. prok ribosomes

A

Eukaryotic ribosome = 40S + 60S subunits = 80S

Prokaryotic ribosome = 30S + 50S = 70S

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8
Q

Describe how scurvy causes signs/symptoms by interaction w/ collagen production

A

Vitamin C is needed by enzyme used in collagen hydroxylation (done in RER before exocytosed)

So vit C deficiency => deficiency in collagen

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9
Q

How does the base composition of DNA alter the melting point

A

CG has a triple bond while AT only has a double bond => the higher the CG content = higher the melting point of the DNA

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10
Q

Fxn of peroxisomes

A

Peroxisomes catabolize very long chain fatty acids, branched chain fatty acids, and amino acids

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11
Q

Briefly explain the molecular mechanism of fatty deposition in liver in alcoholism

A

The enzymatic reaction of ethanol metabolism increases the ratio of NADH / NAD+ in the liver which favors certain reactions including

  • increase glycerol-3 phosphate which combines w/ fatty acids
  • increased acetyl-coA which favors ketogenesis and lipolysis

Basically creates a lot of NADH that needs to get reduced which favors certain reactions cause fatty deposition

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12
Q

MC mutation causing Ehlers-Danlos

(a) Clinical features

A

Ehler-Danlos = CT d/o, MC from mutation in type V collagen

(a) Hyperextensible skin, tendency to bleed (bruise easily), hypermobile joints

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13
Q

What is the mRNA start codon?

(a) What does this code for in eukaryotes?
(b) In prokaryotes?

A

mRNA start codon = AUG
‘AUG’ments translation

(a) Codes for methionine in eukaryotes which is removed before protein synthesis is final
(b) codes for fMet in prokaryotes

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14
Q

Eukaryotic RNA polymerases, functions of

(a) I
(b) II
(c) III
(d) Differences from DNA polymerase

A

Eukaryotes have 3 (not just one) separate types of RNA, numbered in order that their product is used in protein synthesis

(a) RNA I forms rRNA
(b) RNA II forms mRNA
(c) RNA III forms tRNA
(d) RNA polymerases can initiate strand formation, but have no proofreading abilities

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15
Q

Distinguish the 4 types of collagen

A

Collagen I (90%) in bone, skin, tendon, dentin, fascia, cornea, late wound repair

Collagen II: cartilage, nucleus pulposis

Collagen III: reticulin

Collagen IV: basement membrane
-defective in Alports disease, targeted in Goodpastures

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16
Q

What site on tRNA is the amino acid bound to?

A

Amino acid is bound to the 3’ end of tRNA at the 5’ - CCA - 3’ acceptor site

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17
Q

Which type of blotting procedure would be best for

(a) Studying level of gene expression
(b) Confirming positive ELISA test for HIV

A

Blotting tests:
SNoW DRoP

Southern detects DNA
Northern detects RNA
Western detects proteins
Southwestern identifies DNA-binding proteins

(a) Study level expression by quantifying mRNA = Northern blot
(b) Confirm by detecting protein made by HIV virus, protein detected by Western blot

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18
Q

What part of the cell cycle is regulated by

(a) Tumor suppressor genes
(b) cyclin-CKD

A

Cell cycle

(a) Tsgs prevent cells in G0 (non-dividing stage) from entering G1 (growing phase that then leads to S-phase)
(c) Cyclin-cyclin dependent kinases: cyclin activates CKDs, then complex phosphorylates other proteins to coordinate cell cycle progression at all steps

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19
Q

Folate vs. cobalmin deficiency

(a) Anemia
(b) Neurologic symptoms
(c) Homocystine and MMA levels
(d) Which is more common?

A

B9 vs. B12 deficeincy

(a) Both cause megaloblastic anemia
(b) B12 deficiency has neurologic symptoms (subacute combined degeneration) while B9 deficiency doesn’t
(c) Folate (B9) deficiency => elevated homocyestine, normal MMA
B12 deficiency => elevated both homocysteine and MMA
(d) Folate deficiency more common b/c large B12 stores in liver

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20
Q

What is ergosterol?

(a) Drug target for what?

A

Ergosterol = sterol in the cell membranes of fungi, acts as cholesterol does in eukaryotes to keep the plasma membrane fluid

(a) Anti-fungals can act to inhibit the enzymes that make ergosterol => fungi can’t live

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21
Q

Describe the calculations for frequency of the following for a population in Hardy-Weinberg equilibrium

(a) homozygosity for allele p
(b) homozygosity for allele q
(c) heterozygosity

A

Hardy-Weinberg equilibrium

p2 + 2pq + q2 = 1, p + q = 1

(a) p2
(b) q2
(c) 2pq

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22
Q

Chromosomal abnormality of what number leads to

(a) NF1
(b) NF2
(c) DiGeorge

A

(a) NF1 = chrom 17
(b) NF2 = chrom 22
(c) DiGeorge = 22q11 (‘catch 22”) on chrom 22

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23
Q

Duchenne muscular dystrophy

(a) Mode of inheritance
(b) Classic clinical features
(c) Age of onset
(d) Cause of death

A

DMD

(a) X-linked recessive
(b) Gower’s sign, calf pseudohypertrophy
(c) Before age 5
(d) Dilated cardiomyopathy
- b/c dystrophin is needed in both skeletal and cardiac muscle to anchor intra and extracellular matrix

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24
Q

Retinol

(a) Fxn
(b) Clinical features of deficiency
(c) Contraindication to vit A derivative

A

Retinol = vit A

(a) antioxidant, visual pigments
(b) Night blindness, corneal degeneration, scaly skin, immunosuppression
(c) Pregnancy
- isotrentin can cause cleft palate and cardiac abnormalities if taken during pregnancy (teratogen)

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25
Q

Chromatin

(b) What type of chromatin is transcribed?
(c) What type of chromatin are histone bodies?

A

Chromatin = condensed DNA

(a) Euchromatin is transcribed
(b) Histone bodies and other transcriptionally inactive chromatin = heterochromatin

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26
Q

Describe the calculations for frequency of the following for a population in Hardy-Weinberg equilibrium

(a) X-linked recessive disease in males
(b) X-linked recessive disease in females

A

Hardy-Weinberg equilibrium

p2 + 2pq + q2 = 1, p + q = 1

(a) males = q
(b) females = q2 (b/c ned two copies)

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27
Q

Clinical features of familial hypercholesterolemia

A

Familial hypercholesterolemia = mutation/deletion in LDL-receptor

  • severe early atherosclerotic disease
  • cornea arcus
  • tendon xanthomas (classically in Achilles tendon)
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28
Q

What is a microarray?

A

Microarray = grid containing DNA or RNA probes to scan amount of complementary binding

Used for genotyping, forensics, genetic linkage, cancer mutations

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29
Q

Name the 4 trinucletoide repeat d/o

A

“Help memorize frinucl fre-peat”

  • Huntington’s
  • Myotonic dystorphy
  • Friderich’s ataxia
  • Fragile X
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30
Q

D/o of what chromosome causes Wilms tumor

A

Chrom 11

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31
Q

Name the 3 stop codons

A

UGA, UAA, UAG

U Go Away
U Are Away
U Are Gone

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32
Q

2 tests used to confirm dx of Duchenne muscular dystrophy

A

Western blot for lack of dystrophin protein

Muscle biopsy

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33
Q

Where does the energy to form the peptide bone during protein synthesis come from?

A

ATP catalyzes covalent bond btwn amino acid and CCA 3’ end of tRNA molecule

Then during translation the energy of this covalent bond is used by the ribozyme (rRNA) to form peptide bond

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34
Q

What is Lisch-Nyhan Syndrome

(a) Etiology
(b) Clinical features

A

Lisch-Nyhan Syndrome

(a) Aut recessive loss of HGPRT gene needed for purine salvage => purines shunted to uric acid
(b) HGPRT
- hyperuricemia
- gout (sometimes called juvenile gout)
- Pissed off (hallmark feature = multination, aggression)
- retardation (ID)
- tonia (dystonic)

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35
Q

Differentiate etiology of Duchenne and Becker muscular dystrophy

(a) Which is more severe?
(b) Age of onset

A

Both Duchenne and Becker are X linked mutations in dystrophin

  • Duchennes is a frameshift mutation => truncated, nonfunctional protein
  • Beckers is a non-frameshift mutation => partially functional dystrophin

(a) Duchennes is much more severe
(b) Duchennes comes on before age 5, Beckers onset in adolescence

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36
Q

What part of the cell cycle are the following cells in

(a) Hepatocytes
(b) Bone marrow
(c) Neurons
(d) Skeletal and cardiac muscles
(e) Gut epithelium
(f) Hair follicles
(g) RBCs
(h) Lymphocytes
(i) Germ cells

A

Permanent cells (stuck in G0, only regenerate from stem cells) = neurons, skeletal and cardiac muscle, RBCs

Stable/quiescent cells (enter G1 from G0 when stimulated) = hepatocytes, lymphocytes

Labile (never enter G0, rapidly divide w/ short G1) = bone marrow, gut epithelium, hair follicles, germ cells
-most affected by chemotherapy

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37
Q

Clinical picture of Kwashiokor

A

Skinny kid w/ huge abdomen: due to a protein deficiency MEAL

Malnutrition
Edema 2/2 loss of oncotic pressure
Anemia
Liver (fatty) b/c of reduced apolipoprotein production

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38
Q

Differentiate the 4 kinds of blotting procedures

A

SNoW DRoP

Southern detects DNA
Northern detects RNA
Western detects proteins
Southwestern identifies DNA-binding proteins

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39
Q

Fxn of proteasomes

(a) Possibly implicated in what disease process?

A

Proteasome = protein complex that degrades damaged or ubiquitin-tagged protein

(a) Defective proteasomes possibly implicated in Parkinsons

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40
Q

Explain Prader-Willi syndrome

(a) Imprinting
(b) Where is the deletion?
(c) Clinical features
(d) 25% uniparental disomy of which parent?

A

Prader-Willi syndrome

(a) Imprinting = turning off of a gene. In Prader-Willi the maternal copy of the gene is imprinted (turned off), and the paternal copy is either mutated or deleted => disease
(b) Deletion is of the paternal allele
(c) Hyperphagia => obesity, intellectual disability, hypogonadism, hypotonia
(d) 25% cases due to maternal uniparental disomy- where both copies are from mom (so no active paternal copy => disease)

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41
Q

Clinical features of hereditary hemorrhagic telangiectasia

A

Inherited BV disease => branching of skin lesions (telangiectasias)

  • recurrent epistaxis (nose bleed), skin discolorations (easy bruising)
  • AV malformations
  • increased risk of GI bleed and hematuria
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42
Q

Name the assumptions of the Hardy-Weinberg principles for population genetics

A

For populations in Hardy-Weinberg equilibrium: p2 + 2pq + q2 = 1, p + q = 1

Assumptions

  • no mutations occur
  • no net migration (nothing in or out)
  • completely random mating
  • natural selection is not occurring at this locus
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43
Q

Chromosomal d/o of chrom 7

A

Chrom 7 = Williams syndrome (heart defect and abnormal facies)

Cystic fibrosis

44
Q

Thiamine

(a) Main fxn
(b) 3 syndromes that are consequence of deficiencyThiamine

A

Thiamine = B1

(a) Cofactor for enzymes needed to breakdown glucose
(b) Wernicke-Korsakoffs, wet and dry beriberi

45
Q

What is elastin?

(a) Locations
(b) What breaks down elastin?

A

Elastin = stretchy protein

(a) Lungs, skin, large arteries, stretchy ligaments, vocal cords
(b) Elastin is broken down by elastase, elastase constitually inhibited by alpha-1 antitrypsin

46
Q

Protein synthesis at ribosome

(a) Describe initiation
(b) Describe termination

A

Protein synthesis

(a) Initiation by GTP hydrolysis of tRNA, initiation factors assemble the 40S (small ribosomal subunit) w/ initiator tRNA
- then the IFs are released when the 60S binds

(b) Stop codon is recognized by release factors and ribosomal structure dissociates

47
Q

Explain the difference btwn phases of the cell cycle for permanent, stable, and labile cell types

A
  • permanent cell types remain in G0 and will regenerate only from stem cells (not replicate itself)
  • stable/quiescent cells are in G0 but can enter G1 when stimulated
  • labile cells never go into G0, divide rapidly w/ a short G1 (most affected by chemotherapy)
48
Q

Fxn of the golgi apparatus

A

Golgi apparatus = traffics proteins and lipids from the ER to vesicles or the plasma membrane
-also does a lot of processing/adding components

49
Q

Function of RNA polymerase in prokaryotes

(a) Target of what drug?

A

RNA polymerase- one large multi-unit type in prokaryotes that functions to make all 3 types of RNA

(a) Target of rifampin

50
Q

What is the function of intracellular chaperone proteins?

A

Chaperone proteins facilitate and maintain protein folding

51
Q

Differentiate dry and wet beriberi

A

Both are from thiamine (B1) deficiency

Dry beriberi => abnormalities of peripheral nervous system
-polyneuritis, symmetric muscle wasting

Wet beriberi => high output cardiac failure (dilated cardiomyopathy) and capillary wall weakening causing edema

52
Q

What part of protein synthesis uses

(a) ATP
(b) GTP

A

Protein synthesis

(a) ATP used to ‘charge’ the tRNA, aka covalently bond amino acid to 3’ end of tRNA
- done by aminoacyl-tRNA synthetase

(b) GTP is the energy source for translocation of tRNA from A to P site of ribosome

53
Q

What kind of DNA mutation results in

(a) Sickle cell disease
(b) Duchenne’s muscular dystrophy

A

(a) SCD from missense mutation- one amino acid is altered

(b) DMD from frameshift mutation- addition or deletion that ruins 3 pairs => truncated nonfunctional protein

54
Q

Fxn of DNA polymerase I vs. DNA polymerase III

A

Both are only in prokaryotes.

DNA pol III elongates leading strand (adding to 3’ end) and elongates lagging strand. Has 3’ to 5’ exonuclease activity to proofread added nucleotides

DNA pol III degrades RNA primer to replace it w/ DNA

55
Q

Chromosomal d/o of chrom 3

A

Von-Hippel-Lindau disease (pheo, hemangioblastoma)

Renal cell carcinoma

56
Q

Kid who is extremely friendly w/ strangers, ‘elfin’ facies, ID, and hypercalcemia

A

Williams syndrome = microdeletion of chrom 7

Deleted region includes elastin gene => ‘elfin’ faces
Hypercalcemia 2/2 increased sensitivity to vit D

57
Q

Differentiate enhancer and promoter regions of a eukaryotic gene

A

Enhancer region = where transcription factors bind
-can be close, far, or even in intron region of gene

Promoter region = where RNA pol II binds

  • TATA box
  • close/just upstream from gene
58
Q

Nucleoside vs. nucleotide

A

Nucleoside = Base + sugar

Nucleotide = Base + sugar + phosphate

59
Q

2 fxns of the smooth ER

(a) Examples of cell types w/ tons of smooth ER

A

Smooth ER: production of steroids and dotox of chemicals/toxins

(a) Steroid producing cells of the adrenal cortex and gonads.
Detox cells of the liver (hepatocytes)

60
Q

Describe how impaired copper absorption can cause growth retardation and brittle, kinky hair

A

Copper is a necessary co-factor for enzyme used in collagen synthesis

Menkes disease = impaired Cu absorption => inability to crosslink collagen => brittle, kinky hair, growth retardation, and hypotonia

61
Q

Rough ER

(a) What is RER called in neurons?
(b) Name 2 types of cells where RER is especially abundant

A

Rough ER

(a) RER in neurons = Nissl bodies
(b) Cells that have high protein production/secretion
- mucus-secreting goblet cells in small intestines
- antibody producing plasma cells

62
Q

Differentiate the actions of fomeprizole and disulfram on ethanol metabolism

A

Rxn: Ethanol –> (alcohol dehydrogenase) –> Acetaldehyde –> (acetaldehyde dehydrogenase) –> Acetate

Acetaldehyde is the molecule that causes hangover symptoms

  • Fomeprizole (used in EtOH toxicity) inhibits alcohol dehydrogenase to decrease acetaldehyde production
  • Disulfram (= Antabuse) inhibits acetaldehyde dehydrogenase so acetaldehyde builds up => worse hangover = aversion therapy!
63
Q

Elastin activity in

(a) Marfan syndrome
(b) Emphysema

A

Elastin = stretchy protein in lungs, vocal cords, large arteries, skin

(a) Marfan = defect in glycoprotein (fibrillin) that forms a sheath around elastin
=> super stretchy skin and weak arteries (high risk of dissection)

(b) Emphysema = overactive elastase or can be caused early by alpha-1 antitrypsin

64
Q

Elastin activity in

(a) Marfan syndrome
(b) Emphysema

A

Elastin = stretchy protein in lungs, vocal cords, large arteries, skin

(a) Marfan = defect in glycoprotein (fibrillin) that forms a sheath around elastin
=> super stretchy skin and weak arteries (high risk of dissection)

(b) Emphysema = overactive elastase or can be caused early by alpha-1 antitrypsin

65
Q

Describe the enzyme terminology

(a) Kinase
(b) Phosphorylase
(c) Phosphatase
(d) Dehydrogenase
(e) Mutase

A

(a) Kinase: adds P+ using ATP
(b) Adds P+ onto substrate w/o using ATP
(c) Phosphatase- removes P+
(d) Dehydrogenase: catalyzes oxidation-reduction reactions
(e) Mutase: relocates a functional group w/in a molecule

66
Q

Chromosomal d/o of chrom 9

A

Friedreich ataxi

67
Q

Name the 5 features of 22q11 deletion syndromes

A

‘CATCH-22’, due to aberrant development of 3rd and 4th branchial pouches

Cleft palate
Abnormal facies
Thymic aplasia => T cell deficiency
Cardiac defects
Hypocalcema 2/2 parathyroid aplasia

=DiGeorge syndrome, velocardiofacial (palate, facial, cardiac) syndrome

68
Q

CF

(a) Location of mutation
(b) Explain physiology of thick mucus
(c) Newborn screening

A

Cystic fibrosis

(a) Chrom 7 = CFTR gene, MC F508D
(b) CFTR gene codes for ATP-dependent Cl- channel needed to secrete Cl- in lungs/gut and reasorb Cl- in sweat glands
- increase in intracellular Cl- which draws in salt and water => get abnormally thick mucus in lungs and GI tract
(c) Newborn screen using immunoreactive trypsinogen = pancreatic enzyme precursor elevated in CF babies regardless if pancreatic disease has developed yet

69
Q

CF drugs

(a) Which drug to loosen mucus
(b) Activity of DNA-ase

A

CF drugs

(a) NAC (N-acetylcystein)…yes the same one for acetaminophen overdose…used to loosen mucus
-works by cleaving the disulfide bone w/in mucus glycoproteins
(b) DNAase acts to clear leukocytic debris
=Dornase alfa (pulmozyme)

70
Q

2 syndromes that can be caused by a Robertsonian translocation

A

Downs (trisomy 21) and Patau (trisomy 13)

Robertsonian translocation = when the long arms of 2 acrocentric chromosomes (ones w/ centromere at the ends) fuse and the short arms are lost => chromosomal imbalance

71
Q

What is the function of the lac operon on prokaryotes?

A

Lac operon = lactose metabolism protein activated when preferred energy source (glucose) isn’t present to cause up-transcription of lactose metabolism proteins

Prokaryotic genes responding to environment

72
Q

Which type of single stranded DNA repair is defective in

(a) Xeroderma pigmentosum
(b) HNPCC

A

DNA repair

(a) Xeroderma pigmentosum- defective nucleotide excision repair
(b) HNPCC- defective mismatch repair

73
Q

Wernicke-Korsakoff

(a) Triad of clinical features
(b) Brain structure visibly damaged on imaging

A

Wernicke-Korsakoff

(a) Confusion, opthalmoplegia, ataxia
(b) Mammillary bodies

74
Q

Differentiate variable expressivity from incomplete penetrance

A

Variable expressivity: pt w/ same genotype have dif phenotypes
ex: Pts w/ NF1 having dif neurofibromas

Incomplete penetrance: some (but not all) w/ mutant genotype have mutant phenotype
ex: Not all pts w/ BRCA1 mutation develop breast/ovarian cancer

75
Q

Purine vs. pyrimidines

(a) Which bases
(b) Number of rings

A

Purines

(a) A, G
(b) 2 rings

Pyrimidines

(a) T, U, C
(b) 1 ring

76
Q

In which direction do the following occur

(a) DNA synthesis
(b) RNA synthesis
(c) mRNA translation
(d) Protein synthesis

A

Direction

(a,b) DNA and RNA synthesis occurs in 5’ to 3’ direction

  • triphosphate bond on 5’ end provides the energy for the bond to be made, 3’ OH is what attacks the 5’ triphosphate bond
    (c) mRNA is translated from 3’ to 5’ in order to translate
    (d) proteins from N to C terminus
77
Q

Describe how RNA splicing is targeted in SLE

A

RNA splicing (removing introns and combining exons) done by snRNPs (small nuclear ribonuclear proteins) that form spliceosome

Anti-snRNP antibodies = anti-Smith = specific for SLE

78
Q

Do the following occur in the mitochondria or cytoplasm?

(a) FA synthesis
(b) FA oxidation
(c) cholesterol synthesis
(d) ketogenesis
(e) glycolysis

A

(a) FA synthesis in the cytosol
(b) Then FA oxidation in the mitochondria
(c) Cholesterol synthesis in cytosol
(d) Ketogenesis in mitochondria
(e) Glycolysis in cytosol

79
Q

Differentiate the types of proteins made in rough ER vs. free ribosomes

A

Rough ER makes proteins that are excreted from the cell or used at the plasma membrane

Proteins made in free ribosomes act in the cytosol or in organelles

80
Q

Anemia as a consequence of

(a) Vit E deficiency
(b) Vit B12 deficiency

A

Anemia in

a) VitE deficiency = hemolytic anemia
(b) B12 deficiency = megaloblastic anemia (large cells

81
Q

Chromosomal d/o of chrom 5

A

Cri-du-chat syndrome (microdeletion of chrom 5) => microcephay, ID, high pitched cry/mew

FAP (familial adenomatous polyposis)

82
Q

Histones

(a) What charge are histones?
(b) Activity on histones to inhibit transcription
(c) Activity on histones to stimulate transcription

A

Histones

(a) Positively charged to bind to negatively charged DNA
(b) Histone methylation works to inhibit transcription
(c) Histone acetylation acts to stimulate transcription

83
Q

When would you suspect uniparental disomy?

A

Uniparental disomy = both copies of one chromosome is from the same parent

Consider it when offspring manifests a recessive d/o w/ only one parent as a carrier

84
Q

Chromosomal d/o of chrom 4

A

ADPKD w/ PKD2 defect (ADPKD w/ DPK1 defect is chrom 16)

Huntington disease

85
Q

What is telomerase?

(a) Fxn
(b) Fxn in prokaryotes

A

Telomerase = RNA-dependent DNA polymerase (makes DNA off RNA code)

(a) Add DNA to the 3’ end of chromosomes to avoid loss of genetic material w/ every duplication
(b) None…only in eukaryotes

86
Q

MC mutation causing osteogenesis imperfecta

(a) 4 clinical features

A

Osteogenesis imperfecta = variety of genetic bone diseases, MC aut dom mutation causing reduced formation of otherwise normal type I collagen

(a) Type I collagen used in bone, dentin, skin, cornea
- multiple fractures
- blue sclera
- hearing loss (ossicles are abnormal)
- dental imperfections

87
Q

Chromosomal d/o of chrom 5

A

Cri-du-chat syndrome

FAP (familial adenomatous polyposis)

88
Q

Which lysosomal storage disease is not autosomal recessive?

A

All except Fabry disease are autosomal recessive

Fabry disease = X-linked recessive
While Gaucher (MC), Neimann-Pick, Tay-Sachs, Krabbe are autosomal recessive, Metachromatic Leukodystrophy
89
Q

Clinical features of Fabry disease

A

Fabry disease 2/2 lack of alpha-galactosidase A

First features: neuropathyic pain and hypohidrosis (lack of sweat)
Teenage: angiokeratomas and telangiectasias
Later: CV and renal

-highest risk renal failure

90
Q

Clinical features distinguishing Gaucher, Neimann Pick, and Tay-Sachs

A

Both Gaucher and Neimann Pick have hepatosplenomegaly
-no HSM in Tay Sachs

Cherry red spot on macula in Neimann PIck and Tay-Sachs

91
Q

Which lysosomal storage disease carries the highest risk of developing

(a) Renal failure
(b) Ataxia
(c) Optic atrophy

A

(a) Renal failure in Fabry disease (X-linked recessive)
(b) Ataxia seen in metachromatic leukodystrophy due to progressive demyelination
(c) Optic atrophy, seizures, developmental regression in Krabbe disease (galactocerebrosidase deficiency)

92
Q

Dihydrorhodamine flow cytometry reveals absence of green fluorescence characteristic of normal neutrophils

(a) Impaired activity of what enzyme?

A

DHR flow cytometry tests NADPH oxidase fxn of neutrophils

X-linked mutation in NADPH oxidase = impaired respiratory burst and oxidative killing = chronic granulomatous disease

93
Q

Bacteria w/o cell wall

A

Mycoplasma has no cell wall => doesn’t gram stain

94
Q

Limitations to gram stains, so use what other stain to visualize

(a) Treponema
(b) Mycobacteria
(c) Legionella
(d) Rickettsia
(e) Chlamydia

A

(a) Treponema (syphilis) w/ dark field microscopy
(b) Mycobacteria w/ acid fast
(c) Legionella w/ silver stain
-poor visualization b/c primary intracellular
(d,e) Rickettsia and chlamydia (pleomorphic bacteria): visualize w/ Giemsa

95
Q

3 things that stain w/ silver stain

A

Silver stain

  1. Legionella
  2. Fungi (ex: pneumocystis)
  3. H. pylori
96
Q

What is visualized w/ Giemsa stain

A

Giemsa stain for

  • 2 pleomorphic: chlamydia and rickettsia
  • also plasmodium, borrelia, trypanosomes
97
Q

What is visualized by India ink stain?

A

Cryptococcus neoformans

98
Q

Agar to grow

(a) H. influenza
(b) Mycoplasma pneumonia
(c) E. Coli

A

Agar

(a) Chocolate agar (contains factor X hemaglutin and factor V FAD) grows H. influenza and Neisseria
(b) Mycoplasma grows on Eaton agar- b/c contains cholesterol!
- only bacteria w/ cholesterol in cell membrane
(c) E. Coli on EMB agar (eosin-methylene blue agar)

99
Q

Name some urease positive organisms

A

Urease positive organisms

  • Nocardia
  • Klebsiella
  • H. Pylori
  • Cryptococcus
  • Proteus
  • Strep epidermidis and Strep saprophyticus
100
Q

Explain why conjugate vaccines are ‘conjugated’

A

Conjugate vaccines for encapsulated organisms (neisseria meningitis, strep pneumo, H. influenza) meaning polysaccharide capsular antigen is conjugated w/ a protein to cause T-cell response

B/c polysaccharide alone won’t be presented to T cells => no T cell and therefore class switching

101
Q

Which bacteria produce the following color pigments

(a) Yellow
(b) Yellow ‘sulfur’ granules
(c) Red
(d) Blue-green

A

Pigments

(a) Yellow by staph aureus
(b) Yellow ‘sulfer’ granules (granules componse of filaments of bacteria) by actinomyces israelli
(c) Red by serratia
(d) Blue-green by pseudomonas

102
Q

4 bacteria w/ type III secretion system

A

Type III secretion system (injectisome): needle like protein appendage to facilitate direct delivery of toxin from gram negative bacteria into eukaryotic host

  1. E. Coli
  2. Salmonella
  3. Shigella
  4. Pseudomonas
103
Q

Explain mechanism of ADP ribosylating A-B toxin

A

B (binding) component binds to host cell surface receptor for endocytosis

then A (active) component attaches to ADP-ribosyl to disrupt host cell proteins

Most exotoxins (diphtheria, pseudomonas, shiga, cholera, pertussis)

104
Q

2 exotoxins that inactivate EF-2

A
  1. Corynebacterium diptheriae’s diphtheria toxin inactivates elongation factor 2
  2. Pseudomonas’s exotoxin A
105
Q

2 exotoxins that lyse cell membranes

A
  1. Clostridium perfinges’ alpha toxin = lecithinase that degrades tissue and cell membranes => gas gangrene and double zone hemolysis
  2. GAS streptolysin O degrades cell membranes
106
Q

2 bacterial species w/ superantigens that can cause shock

A
  1. Staph aureus: TSST-1
  2. Strep pyogenes (GAS): Exotoxin A

Bind to MHCII and TCR to cause overwhelming release of IL-1, IL-2, IFN-gamma, TNF-alpha

107
Q

2 bacteria toxins that are heat stable

A

All exotoxins except staph enterotoxin are destroyed rapidly over 60 C

While endotoxin (LPS) is crazy heat stable, stable at 100 C for 1 hr

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