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STEP 1 > 11a: Genetics/Nutrition > Flashcards

11a: Genetics/Nutrition Flashcards

1
Q

Histones are rich in which AA?

A

Lys, Arg

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2
Q

(H1/H2/H3/H4) histone is outside the core and acts as linker/stabilizer

A

H1

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3
Q

Heterochromatin: highly (methylated/acetylated).

A

Methylated (low acetylation) - condensed and inactive

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4
Q

Nucleoside is made up of which components? And nucleotide?

A

NucleoSide: base + (deoxy)ribose Sugar
NucleoTide: base + (deoxy)ribose + phosphaTe

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5
Q

Deamination of 5-methylcytosine makes:

A

Thymine

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6
Q

Deamination of guanine makes:

A

Xanthine

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7
Q

Deamination of cytosine makes:

A

Uracil

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8
Q

Deamination of adenine makes:

A

Hypoxanthine

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9
Q

Methylation of uracil makes:

A

Thymine (“THYmine has a meTHYl”)

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10
Q

List the three amino acids necessary for purine synthesis

A

“GAG”
Glycine
Asp
Gln

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11
Q

(CG/AT) bonds are stronger, so higher content of these means (higher/lower) melting T of DNA

A

CG (“C-G bonds are like Crazy Glue”) - have 3 H bonds instead of 2
Higher

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12
Q

First step in de novo pyrimidine base synthesis

A

Gluamine and CO2 -> Carbamoyl phosphate (via Carbamoyl phosphate synthetase II)

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13
Q

Leflunomide inhibits (X) in (Y) pathway

A

X = dihydroorotate dehydrogenase

De novo Pyrimidine synthesis
used as immunosuppressive drug, ex: RA

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14
Q

Hydroxyurea MOA:

A

Inhibits ribonucleotide reductase (in de novo pyrimidine synthesis) so UDP can’t become dUDP

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15
Q

Ribavirin has same target/MOA as which other drug?

A

Mycophenolate (inhibit inosine monophosphate dehydrogenase; decrease IMP to GMP purine formation)

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16
Q

T/F: Low folate means low dUMP and low dTMP

A

False - high dUMP and low dTMP (since it’s that conversion by thymidylate synthase that’s impaired)

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17
Q

PRPP is synthesized from:

A

Ribose-5P (via PRPP synthetase)

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18
Q

GMP is the (nucleotide/nucleoside/free base). What are the other forms named?

A

Nucleotide (has phosphate)
Nucleoside: guanosine
Free base: guanine

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19
Q

Lesch-Nyhan caused by (low/high) (X) enzyme levels

A

Absent

X = HGPRT (defective purine salvage), which normally converts hypoxanthine to IMP and guanine to GMP

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20
Q

Autosomal recessive SCID: impaired/deficiency in (X), which causes disease via what mechanism?

A

X = Adenosine deaminase (converts adenosine to inosine for purine degradation)

In ADA deficiency, high dATP levels causes toxicity in lymphocytes

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21
Q

Child with intellectual disability and “orange sand” in diaper.

A

Lesch-Nyhan (Na urate crystals in diaper due to hyperuricemia)

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22
Q

The genetic code is universal (conserved throughout evolution). What’s the only exception?

A

Mitochondrial DNA

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23
Q

Bloom Syndrome: a disorder caused by impaired (X)

A

X = helicase production (BLM gene mutation)

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24
Q

Only polymerase with 5’-3’ exonuclease activity in prokaryotes

A

DNA Pol I (removes primer)

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25
Q

List the components of telomerase

A
  1. TERT: reverse transcriptase
  2. TERC: code (RNA template) repeatedly read by TERT

Adds DNA to 3’ ends of chromosomes (to avoid genetic material loss during replication)

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26
Q

T/F: Telomerase is only found in eukaryotic cells

A

True (ex: cancer cells, stem cells)

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27
Q

Nonsense mutation means truncated (protein/mRNA).

A

Protein (NOT mRNA! Stop codon added)

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28
Q

Xeroderma pigmentosum: defective (X)

A

X = DNA endonucleases for NT excision repair

So pyrimidine dimers formed by UV light can’t be repaired

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29
Q

List the steps/players in DNA Base excision repair

A
  1. Glycosylase (base-specific; removes altered base and creates apurinic/apyrimidinic site)
  2. Endonuclease (cleaves 5’ end)
  3. Lyase (cleaves 3’ end)
  4. Polymerase-beta (fills gap)
  5. Ligase (seals gap)
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30
Q

Which (DNA/RNA) polymerase is the only one that’s restricted to nucleolus?

A

RNA Pol I (makes rRNA)

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31
Q

Which RNA Pol makes tRNA?

A

RNA Pol III (three makes t, the tiniest RNA)

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32
Q

T/F: There are three different RNA Polymerases in both eukaryotic and prokaryotic cells

A

False - prokaryotes only have on RNA Pol

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33
Q

RNA Processing (capping 5’ end, polyadenylation, splicing) occurs in (X) (before/after) transportation to (Y).

A

X = nucleus
Before
Y = cytoplasm (for translation)

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34
Q

mRNA quality control occurs at (X) in cytoplasm

A

X = Processing (P) bodies

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35
Q

Amino acids are linked by (X) bond(s) to (5’/3’) end of tRNA

A

X = covalent

3’ (CCA)

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36
Q

(X) arm of tRNA contains (Y) sequence, necessary for ribosome binding

A 
X = T-arm ("Tethers" to ribosome)
Y = T𝚿C (ribothymidine, pseudouridine, cytidine)
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37
Q

(X) arm of tRNA contains (Y) sequence, necessary for tRNA recognition by correct aminoacyl-tRNA synthetase

A 
X = D-arm ("Detection" of tRNA by aminoacyl-tRNA synthetase)
Y = dihydrouridine residues
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38
Q

Eukaryotes have which ribosome subunits? And prokaryotes?

A

Eukaryotes have the Even numbers: 40S + 60S = 80S

prOkaryotes have the Odd numbers: 30S + 50S = 70S

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39
Q

tRNA charging with amino acid requires (ATP/GTP)

A

ATP (for “Activation” of tRNA)

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40
Q

Protein synthesis requires (ATP/GTP)

A

GTP (“tRNA Grips mRNA and Goes places”)

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41
Q

Which amino acids are exclusively ketogenic?

A

Lys and Leu (cannot be metabolized to pyruvate)

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42
Q

Hypoketotic hypoglycemia most often a deficiency in (X)

A

X = Acyl-CoA dehydrogenase (first step in beta-ox pathway)

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43
Q

First (rate-limiting) step in FA synthesis

A

Acetyl-CoA decarboxylase

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44
Q

N-acetylglucosaminyl-1-phosphotransferase defect, aka (X) disease, is due to failure of which process?

A

X = I-cell (inclusion cell)
Golgi phosphorylation of mannose residues on glycoproteins (causing them to be extracellularly secreted instead of delivered to lysosomes)

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45
Q

COPI and COPII involved in which steps of cell trafficking?

A

COPII: anterograde from RER to cis-Golgi
COPI: retrograde from cis-Golgi to RER

(“Two steps forward, One step back”)

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46
Q

Membrane-enclosed organelle involved in catabolism of (X) fatty acids, amino acids, and EtOH

A

Peroxisome

X = very-long-chain and branched-chain

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47
Q

Peroxisomal disorders commonly lead to (X) manifestations/symptoms due to deficits in synthesis of (Y)

A 
X = neuro
Y = plasmalogens (important phospholipids in myelin)
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48
Q

Cilia are (microfilaments/intermediate filaments/MTs)

A

MTs

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49
Q

Microvilli are (microfilaments/intermediate filaments/MTs)

A

Microfilaments

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50
Q

Vimentin is example of (microfilaments/intermediate filaments/MTs) found in (X)

A

Intermediate filaments;

X = mesenchymal tissue (fibroblasts, endothelial cells, macros)

51
Q

GFAP and cytokeratin are (microfilaments/intermediate filaments/MTs)

A

Intermediate filaments

52
Q

Desmin is example of (microfilaments/intermediate filaments/MTs) found in (X)

A

Intermediate filaments

X = muscle (ex: rhabdomyosarcoma stains positive for desmin on immunohistochem)

53
Q

Bronchiectasis, recurrent sinusitis, chronic ear infections, and (conductive/sensorineural) hearing loss due to (AD/AR) defect leading to immotile cilia.

A

Kartagener syndrome (also situs inversus); issue with dynein arm in cilia

Conductive; AR

54
Q

Collagen mRNA undergoes the next few steps in which cell compartment? What are the steps?

A

RER

  1. Translation (into Preprocollagen)
  2. Hydroxylation of proline and lysine (needs vit C)
  3. Glycosylation of hydroxylysine
  4. Procollagen triple helix formation (H and disulfide bonds between 3 collagen alpha chains)
55
Q

Procollagen eventually enters (X) compartment for which subsequent steps, leading to final collagen formation?

A

X = extracellular (leaves cell)

  1. Proteolytic processing and cleavage of terminal regions (via procollagen peptidases; forms insoluble tropocollagen)
  2. Cross-linking (covalent lysine-hydroxylysine bonds by lysyl oxidase; needs Cu)
56
Q

Which step(s) in (X) synthesis is/are impaired in ehlers-danlos?

A

X = Collagen

Either of the extracellular steps (proteolytic processing or covalent cross-linking by lysyl oxidase)

57
Q

T/F: Most common form of osteogenesis imperfecta is AD with defective Collagen I

A

False - the collagen is normal, but there is just decreased production

58
Q

Classical type of Ehlers-Danlos: mutation in type (X) collagen. And vascular type is mutation in (Y) collagen

A 
X = V (joint/skin symptoms; within dermal/epidermal junction)
Y = type III (vascular and organ rupture)
59
Q

Menkes disease:

A

X-linked recessive impaired Cu absorption/transport (low lysyl oxidase activity)

Brittle hair, growth retardation, hypotonia

60
Q

T/F: Niacin can be synthesized endogenously

A

True - from Tryphtophan

61
Q

Amino acid transamination reactions: which cofactor required?

A

B6 (pyridoxine)

62
Q

5 year old boy with developmental delay, elongated limbs, bilateral lens subluxation. Dies from massive stroke. Dx?

A

Homocystinuria

63
Q

Elastin is rich in which (hydroxylated/nonhydroxylated) AA residues?

A

Non-hydroxylated

Lys, Gly, Pro

64
Q

The effect of UV(A/B) wavelengths on aging/wrinkles is due to (increase/decrease) (collagen/elastin)

A

UVA
Decrease
Collagen and elastin production (due to ROS and inflammation)

65
Q

(X) is a glycoprotein that forms a sheath around (collagen/elastin)

A

X = fibrillin

Elastin (defective in Marfan syndrome)

66
Q

RT-PCR is used for what purpose?

A

To ID specific mRNA sequence (uses reverse transcriptase to create cDNA and then amplify that by PCR)

67
Q

Microarrays are used to detect:

A

Relative amounts of DNA or RNA probe complementary binding (ex: gene expression levels) of thousands of genes simultaneously

68
Q

Example of Co-dominance

A

Blood groups (A, B, AB) - both alleles contribute to phenotype

69
Q

Two patients with NF-1 have different disease severity. Which phenomenon?

A

Variable expressivity

70
Q

McCune-Albright syndrome is either lethal or survivable, depending on:

A

Whether mutation affects all cells (occurs before fertilization; lethal) or whether mosaicism is present

71
Q

List the law assumptions of Hardy-Weinberg

A
  1. Random mating
  2. No natural selection
  3. No net migration
  4. No mutations at locus
72
Q

As the distance between a gene and linkage marker gets smaller, recombination frequency approaches:

A

0%

73
Q

LOD score refers to probability that:

A

A particular gene and marker are linked (higher score associated with more accurate recombination frequency in table)

74
Q

Prader-willi: (maternal/paternal) gene deleted

A

Paternal (so maternal imprinting; gene from mom normally silent)

75
Q

List three key examples of X-linked dominant disorders

A
  1. Hypophosphatemic rickets (vit D-resistant; PO4 wasting at prox tubule)
  2. Fragile X
  3. Alport syndrome
76
Q

CF: newborn screen detects (X)

A

X = immunoreactive trypsinogen (IRT)

Which is released into blood when pancreas is damage

77
Q

CF: (high/low) chloride levels in primarily which organs?

A

Low in pancreas and lungs (can’t be secreted; so water isn’t pulled in to thin out secretions)
High in sweat (can’t be reabsorbed; skin tastes salty)

78
Q

Explain the Nasal Transepithelial Potential Diff Test for (X) disease

A

X = CF

Normal saline applied to nasal mucosa&raquo_space; high Na reabsorption, Cl retained in lumen&raquo_space; more negative transepithelial potential difference than normal

79
Q

CF patient can present with (acidosis/alkalosis) and (hyper/hypo)-kalemia. Why?

A

Alkalosis (contraction) and hypokalemia - ECF effects analogous to patient on loop diuretic;

ECF H2O/Na losses causes concomitant renal H/K wasting

80
Q

Two key pathogens responsible for recurrent pulm infections in CF patients are:

A
  1. S. aureus (in early infancy)

2. P. aeruginosa (in adolescence)

81
Q

Congenital bilateral absence of vas deferens (CBAVD) is strongly associated with:

A

CF

82
Q

T/F: Hypertonic saline is used to treat CF

A

True (facilitates mucous clearance); salt supplementation recommended for all CF patients

83
Q

Becker versus Duchenne muscular dystrophies

A

Both X-linked mutations in dystrophin gene

Duchenne: frameshift or nonsense mutation leading to absent dystrophin protein (early onset, more severe)

Becker: non-frameshift mutations with partially functional protein (later onset in adolescence/early adulthood)

84
Q

Lyonization is:

A

F carriers of X-linked R disorders can be affected/symptomatic depending on pattern of X inactivation

85
Q

Function of dystrophin protein

A

Links intracellular actin to dystrophin-associated protein complex (which is anchored to ECM); stabilized sarcolemma (muscle cell membrane)

86
Q

Myotonic dystrophy: (AR/AD/X-linked) disorder with which key symptoms?

A 
AD tri-NT repeat (CTG)
"CTG":
1. Cataracts
2. Toupee (early balding)
3. Gonadal atrophy

And muscle atrophy/myotonia obv

87
Q

List the key genetic diseases that arise from trinucleotide repeat expansion

A

“Tri (NT) HUNTING for MY FRAGILE cage-FREE eggs (X)”

  1. Huntington’s (CAG - “Caudate with low Ach and Gaba”)
  2. Myotonic dystrophy (CTG - “Cataracts, Toupee, Gonad atrophy”)
  3. Fragile X (CGG - “Chin (protruding), Giant Gonads”)
  4. Friedreich ataxia (GAA - “ataxic GAAit”)
88
Q

First trimester serum screen findings for Down syndrome:

A

Low PAPP-A, high free beta-hCG

89
Q

Second trimester serum screen findings for Down syndrome:

A

Low alpha-fetoprotein and estriol

High beta-hCG and inhibin A

90
Q

All serum screens in first/second trimester (PAPP-A, beta-hCG, alpha-fetoprotein, estriol, inhibin A) are low. Which genetic syndrome?

A

Edwards

91
Q

46, XX, 5p-

A

Cru di chat (congenital deletion of short arm of chromosome 5)

92
Q

Cleft palate, bifid uvula, and cardiac defects : (X) syndrome

A

X = DiGeorge

93
Q

Pantothenic acid

A

Vit B5 (component of CoA)

Think “PENTOthenic acid”

94
Q

List the essential AAs. Star the one(s) only essential in certain cases.

A

“PVT TIM HALL”

  1. Phe
  2. Val
  3. Thr
  4. Trp
  5. Ile
  6. Met
  7. His
  8. Arg* (only when there’s pos nitrogen balance)
  9. Leu
  10. Lys
95
Q

Active sites of enzymes. Which AA comes to mind?

A

His

96
Q

Homocysteine produced from:

A

Met (after it donates 1 methyl group)

97
Q

Triangular white or yellowish foamy spots on bulbar conjunctiva (either side of cornea)

A

Bitot spots; keratinizing squamous metaplasia of conjunctiva (seen in vit A deficiency)

98
Q

Vit A found in which food sources?

A

Liver and leafy veggies

99
Q

Thiamine is cofactor for:

A

Dehydrogenases (Pyruvate, alpha-KG, branched-chain ketoacid) and transketolase

100
Q

Riboflavin is important for which two key enzymes/processes?

A

(Vit B2; component of FAD, FMN)

  1. Succinate dehydrogenase (TCA)
  2. Complex II (ETC)
101
Q

Which vitamins are required for niacin synthesis?

A

B2 (riboflavin) and B6 (pyridoxine)

102
Q

List 3 main causes of niacin deficiency (apart from decreased intake)

A
  1. Hartnup disease (decreased Trp reabs in kidney/gut)
  2. Carcinoid syndrome (high Trp metabolism)
  3. Isoniazid use (due to low vit B6)
103
Q

Diarrhea, rash/hyperpigmentation, and high neutral AA in urine

A

Hartnup disease (AR eficiency in neutral AA transporters in PCT kidney and on enterocytes; leads to pellagra)

104
Q

Hartnup disease Rx:

A

High protein diet and niacin/nicotinic acid supplementation daily

105
Q

Niacin toxicity/excess:

A

Flushing (caused by PGE), hyperglycemia, hyperuricemia

106
Q

Vit (X): essential cofactor for acyl transfers and FA synthase

A

X = B5 (pantothenic acid; component of CoA)

107
Q

AA important in transamination reactions

A

B6

108
Q

AA important in decarboxylation and glycogen phosphorylase reactions

A

B6

109
Q

Convulsions, hyperirritability, and peripheral neuropathy: which vit deficiency?

A

B6

110
Q

Sideroblastic anemia: which vit deficiency?

A

B6

111
Q

Biotin cofactor for:

A 
(vit B7)
Carboxylation enzymes (pyruvate carboxylase, acetyl-coa carboxylase, propionyl-coa carboxylase)
112
Q

Vit B(X) deficiency may cause metabolic acidosis. Why?

A

X = 7 (biotin)

High pyruvate levels (can’t be converted to oxaloacetate via pyruvate carboxylase) causes lactic acid buildup

113
Q

Homocysteine to cysteine: which vit required?

A

B6

114
Q

Homocysteine to methionine: which vit required?

A

B12 (enzyme: Met synthase)

115
Q

B12 required for synthesis of (X)-CoA from (Y)-CoA.

A

X = succinyl
Y = methylmalonyl
(enzyme: methylmalonyl-coa mutase)

116
Q

Synthesis of heme from (X) requires vit B(Y)

A 
X = Succinyl-CoA
Y = 6 (pyridoxine)
117
Q

Vitamin C facilitates (X) absorption and is necessary for which NT synthesis?

A

X = Fe (by reducing it to Fe2+ state)

NE from Dopamine (enzyme: dopamine beta-hydroxylase)

118
Q

Hemolytic anemia, muscle weakness, posterior column and spinocerebellar tract demyelination. Vit (X) (deficiency/excess).

A

X = E
Deficiency

Similar to vit B12 deficiency but without megalobl. anemia/hyperseg PMNS or high serum methylmalonic acid

119
Q

Delayed wound healing, hypogonadism, and decreased adult hair (axillary, facial, pubic). Caused by (X) nutritional (deficiency/excess)

A

X = Zn

Deficiency

120
Q

Anosomia and dysgeusia (distorted taste). Caused by (X) nutritional deficiency

A

X = Zn

121
Q

Fomepizole inhibits (X) and is used for (Y)

A 
X = alcohol dehydrogenase (EtOH to acetaldehyde rxn)
Y = overdoses of MeOH or Ethylene glycol

“FOMEpizole is For Overdose of Methanol or Ethylene glycol”

122
Q

Disulfuram inhibits (X) and is used for (Y)

A 
X = acetaldehyde dehydrogenase (acetald. to acetate rxn)
Y = discourage drinking (buildup of acetald causes hangover sx)
123
Q

EtOH metabolism: what’s the limiting reagent?

A

NAD+

STEP 1 (21 decks)

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