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Evan's Step 1 Prep Material > Molecular EC > Flashcards

Molecular EC Flashcards

1
Q

Which is transcriptionally active: heterochromatin or euchromatin?

A

Euchromatin is active

HeteroChromatin is Highly Condenced

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2
Q

What do DNA methylation and acetylation do?

A

Methylation makes DNA Mute (inactive)

Acetylation makes DNA Active

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3
Q

What amino acids are required for purine synthesis?

A

GAG

Glycine, Aspartate, Glutamine

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4
Q

What does ribonucleotide reductase do?

A

reduces nucleotides to deoxy forms

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5
Q

What cofactors are required for ribonucleotide reductase action?

A

thioredoxin and NADPH

*oxidized thioredoxin reduced/recycled by tioredoxin reductase

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6
Q

What is the rate limiting step of purine synthesis?

A

PRPP synthetase

*converts Ribose-5-P to PRPP

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7
Q

What ensures balance is maintained in purine synthesis? (2 things)

A

Cross regulation (GMP requires ATP and vice versa)

Each pathway has end-product inhibition

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8
Q

What is the rate-limiting step of pyrimidine synthesis?

A

CPS-II (formation of carbamoyl phosphate from CO2, glutamine and ATP)

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9
Q

What nucleotides is IMP a precursor to?

A

AMP and GMP

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10
Q

What nucleotides are UMP a precursor to?

A

CTP and TMP

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11
Q

What converts dUMP to dTMP?

A

Thymidylate synthase

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12
Q

What causes Orotic aciduria?

How does it present?

What is the treatment?

A

Defect in UMP synthase (converts orotic acid to UMP)

Presents as megaloblastic anemia UNRESPONSIVE to B12 or folate

Treat with lifetime uridine supplementation

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13
Q

What is the sequence from AMP to Uric acid?

A

AMP–>Adenosine–>Inosine–>Hypoxanthine–>Xanthine–> Uric acid

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14
Q

What is the sequence from GMP to Uric acid?

A

GMP–>Guanine–>Xanthine–>Uric acid

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15
Q

What is SCID?

What is its mechanism?

A

Severe Combined Immunodeficiency Disease

Adenosine deaminase deficiency (inability to convert adenosine to inosine)

  • ATP/GTP imbalance inhibits ribonucleotide reductase
  • prevents DNA synthesis
  • decreased lymphocytes count
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16
Q

What is Lesch-Nyhan syndrome?

What is its mechanism?

What are the findings?

A

Absence of HGPRT (& thus purine salvage)
“He’s Got Purine Recovery Troubles”

Results in excess uric acid production

Retardation
Self-mutilation
Aggression
Hyperurecemia/gout
Choreoathetosis
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17
Q

What is a silent point DNA mutation?

A

a mutation that codes for the same amino acid

often a change in the 3rd a.a. (tRNA wobble)

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18
Q

What is a missense mutation?

A

Wrong amino acid but similar chemical structure

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19
Q

What is a Nonsense mutation?

A

Change resulting in easly STOP codon

“STOP the NONSENSE”

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20
Q

What is a frameshift mutation?

A

Misreading all nucleotides downstream

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21
Q

Where are the p53 and RB genes located?

A

p53 is on chromosome 17

RB is on chromosome 13

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22
Q

Describe Mismatch Repair

A

Mismatch repair enzymes recognize mismatched nucleotides

GATC endonuclease makes incision in daughter strand
Removed and gap filled

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23
Q

Mutations in mismatch repair enzymes gives rise to what disease?

A

HNPCC (hereditary nonpolyposal colorectal cancer)

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24
Q

Describe base excision repair

A

Cytosine is spontaneously deaminated to uracil

Uracil DNA glycosylase removes Uracil

AP endonucleases cut DNA and nucleotide is replaced

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25
Describe nucleotide excision repair
thymidine dimmers caused by UV light are removed by excision endonucleases
26
What is Xeroderma pigmentosum
Caused by a mutation in excision endonucleases responsible for repairing thymidine dimers
27
Describe direct DNA repair
Alkylation agents (temozolide) cause methylation of Guanine. MGMT repairs (permanently inactivated and can be depleted)
28
What is nonhomologous end joining?
Repair of double stranded DNA breaks Caused by iodinizing radiation or free radical oxidation Mutated in ataxia telangiectasia
29
What phase of the cell cycle to 5-FU and Methotrexate act? What is the mechanism?
S-phase specific Inhibit dTMP synthesis to block DNA replication (5-FU inhibits thymidylate synthase) (Methotrexate inhibits DHF reductase)
30
In what part of the cell cycle do Bleomycin and Etoposide act? By what mechanism?
S and G2 phases Inhibit topoisomerase II (preventing strand sepparation)
31
What is the mechanism of Cyclophosphamide and Nitosoureas?
Alkylating agents that lead to copying errors and expression of abnormal proteins
32
What is the mechanism of Doxorubicin and Actinomycin D?
Intercalated into DNA rand block DNA/RNA polymerases
33
What phase of the cell cycle do vinca alkaloids (vincristine and paclitaxel) work? What are their mechanisms?
M-phase specific Vincristine inhibits mitotic spindle formation Paclitaxel inhibits mitotic spindle breakdown
34
BCL2 proto oncogene function and associated tumors
Inhibits apoptosis Mutated in follicular B cell lymphoma
35
ERBB2 proto oncogene function and associated tumors
Binds epidermal growth factor Breast Ovarian Stomach
36
MYC proto oncogene function and associated tumors
Activates transcription Burkitt's Lymphoma Neuroblastoma
37
RAS proto oncogene function and associated tumors
G protein that transducers growth factor signals Bladder Lung Colon Pancreas
38
APC tumor suppressor gene function and associated tumors
Inhibits MYC expression FAP (familial Adenomatous Polyposis) Colorectal cancer
39
BRCA1 and BRCA2 tumor suppressor gene function and associated tumors
DNA repair ``` BRCA1 Breast Ovary Colon Prostate ``` BRCA2 Male and female breast
40
NF1 and NF2 tumor suppressor gene function and associated tumors
Control intra cellular signaling Neurofibromatosis: optic nerve gliomas, meningioma, acoustic neuroma, pheochromocytoma
41
TP53 tumor suppressor gene function and associated tumors
Mediates G1 arrest and apoptosis ``` Li-Fraumeni Breast Brain Leukemia Sarcoma ```
42
RB1 tumor suppressor gene function and associated tumors
Mediates G1 arrest Retinoblastoma Osteosarcoma Breast cancer
43
WT1 tumor suppressor gene function and associated tumors
Represses transcription in developing kidney Wilm's tumor
44
Ataxia telangiectasia
Defective DNA repair (double stranded breaks) Lymphoma Cerebellar ataxia; dilation of blood vessels in skin and eyes Immunodeficiency (B and T cells)
45
Bloom's syndrome
Defective DNA repair Carcinomas, Leukemias, Lymphoma Facial telangiectasia Growth retardation Immunodeficiency
46
Fanconi's anemia
DNA repair defect Leukemia Aplastic anemia Pancytopenia Congenital abnormalities
47
HNPCC (hereditary nonpolyposis colorectal cancer)
Defective DNA repair (mismatch repair) Colon, ovary Tumors before 40
48
Xeroderma pigmentosum
Defective DNA repair (nucleotide excision repair of thymidine dimers) BCC, SCC, malignant melanoma Severe skin lesions
49
What is a pseudogene?
Produced by a retrovirus DNA from mRNA Cannot be expressed (lack promoter and introns)
50
What is a Transposon (jumping gene)?
DNA sequences that insert themselves into different areas of the genome
51
What is a Retrotransposon? What are examples of genetic diseases caused by Retrotransposons?
Jumping genes that use reverse transcriptase Can prevent the expression of normal proteins ei. Hemophilia and Duchenne Muscular Dystrophy
52
What are some drugs that inhibit the G2 phase of the cell cycle?
Etoposide and Bleomycin inhibit the synthesis of tubulin
53
What are some drugs that inhibit the S phase of the cell cycle?
5-FU and Methotrexate Inhibit DNA synthesis
54
What are some drugs that inhibit the M phase of the cell cycle?
Colchicine Paclitaxel Vinca alkaloids
55
What are CDKs and Cyclins?
CDKs phosphorylate proteins and activate them to promote cell cycle progression Cyclins bind CDKs and activate them
56
What are p53 and RB?
p53 inhibits G1 to S progression UN-phosphorylated RB also inhibits G1 to S progression
57
What is DNA Gyrase (topoisomerase II)?
Relaxes NEGATIVE supercoils in DNA replication
58
What is DNA Helicase?
Separates DNA strands
59
What are Single Stranded Binding Proteins?
Prevent strand from re-annealing
60
What is DNA primase?
Makes RNA primer | DNA polymerase III can initiate from
61
What is DNA polymerase III?
Elongates leading strand Exonuclease activity "proofreads"
62
What is DNA ligase?
Seals Okazaki fragments
63
What is telomerase?
Adds DNA to 3' end to maintain chromosome length *somatic cells do not have telomerase-aging*
64
Types of RNA and polymerases used to synthesize
rRNA (rampant) >> RNA polymerase I mRNA (massive) >> RNA polymerase II *inhibited by alpha-amanitin tRNA (tiny) >> RNA polymerase III
65
What antibiotic inhibits prokaryotic RNA polymerase?
Rifampin
66
What are 3 common sequences in the eukaryotic promoter?
TATA (binds TBP) CAAT (binds NF1) CG (binds SP1)
67
hnRNA
primary mRNA transcript containing coding and noncoding sequences (before introns are removed via splicing)
68
What is the purpose of the cap and tail of the mRNA?
7-methylguanosine CAP orients mRNA on the ribosome Poly(A) tail increases the half life
69
snRNPs
aggregate at introns forming spliceosomes SLE - autoantibodies against snRNPs
70
lac operon: Low lactose, low glucose
No transcription Repressors inhibit expression
71
lac operon: High lactose, low glucose
Transcription Allolactose inducer No glucose --> cAMP elevated --> CAP-cAMP complex stimulates transcription
72
lac operon: High lactose, High glucose
No transcription Allolactose inducer Glucose-->cAMP low--> no transcription stimulation *allows glucose to be used up first*
73
Describe drugs resistance in cancer cells due to amplication
The gene for dihydro folate reductase can be increased to levels 3000 times the lethal dose of methotrexate in normal cells.
74
Name two examples of alternative splicing
Fibronectin : extracellular matrix, cell surface, and soluble all from same mRNA *Removal of carboxy-terminal converts from membrane to soluble protein IgG heavy chain in B cells
75
mRNA editing of apolipoprotein B
In the GUT: ApoB-48 do not bind LDLR, encoded not to include binding domain In the LIVER: Apo-100 has LDLR binding domain
76
What are some examples of autosomal dominant diseases?
``` Familial hypercholesterolemia, Marfan's, Osteogenesis imperfecta, Huntington's von Williebrand's Hereditary spherocytosis Adult poly cystic kidney disease Neurofibromatosis ```
77
What are some examples of autosomal recessive diseases?
``` Inborn errors of metabolism Sickle cell Cystic fibrosis Adrenogenital syndrome Wilson's disease ```
78
What are some examples of X lined diseases?
``` Duchenne's muscular dystrophy Fabry's disease Hemophilia A and B Hunter's syndrome Lesch-Nyhan syndrome G6PD deficiency ```
79
What antibiotics work on the 30S subunit?
Tetracyclins: Bind 30S and block incoming aminoacyl tRNA Aminoglycosides: Inhibit 30S subunit Streptomycin: Inhibit 30S subunit
80
What antibiotics work on the 50S subunit?
Chloramphenicol:Inhibits peptidyltransferase activity of 50S Erythromycin: Inhibits 50S translocation along mRNA Clindamycin: Inhibits 50S translocation along mRNA
81
What are some antibiotics that work on eukaryotic 60S subunit?
Shiga toxin Shiga-like toxin (EHEC) Ricin ~All cleave 28S of 60S subunit which prevents binding of aminoacyl tRNA
82
How does diptheria toxin inhibit protein synthesis?
Inhibits EF-2 (elongation factor 2), inhibiting ribosome translocation
83
What antibiotic targets eukaryotic peptidyl transferase?
Cyclohexamide: fungicidal and rat repellant
84
Describe polypeptide translocation to the RER
Ribosome attaches to ER membrane via SRP Translocon: directs into ER lumen Amino end enters first, signal sequence cleaved Msy be glycosylated in lumen
85
I-Cell disease
Cannot form mannose-6-phosphate on enzymes targeted for lysosomes ~deficient in phosphotransferase needed to add M6P Enzymes produced normally, but secreted into blood instead of lysosome *presents with coarse facial features, clouded corneas, restricted joint movement.
86
Ubiquitin
Tags proteins to be degraded in proteosome
87
Vesicular trafficking proteins
``` COP1: golgi>golgi (retrograde) golgi>ER COPII: golgi>golgi (anterograde) ER>golgi Clathrin:transGolgi>lysosomes plasma membrane>endosomes ```
88
Molecular motor proteins
Dyenein: Retrograde microtubule (+>-) Kinesin: Anterograde microtubule (->+)
89
Chediak-Higashi syndrome
Pyogenic infections Partial albinism Peripheral neuropathy Mutation in lysosome trafficking regulatory gene (LYST)
90
Drugs that act on microtubules
``` Mebendazole/thiabendazole (antihelminthic) Griseofulvin (antifungal) Vincristine/vinblastine (anti-cancer) Paclitaxel (anti breast cancer) Colchicine (anti-gout) ```
91
Kartagener's syndrome
immotile cilia Dyenein arm deficiency Infertility Bronchiectasis Recurrent sinusitis Associated with siatus inversus
92
Drugs that inhibit Na/K pump
Ouabain: inhibits binding to K site ``` Cardiac glycosides (digoxin/digitoxin) directly inhibit ATPase Leads to decreased Na/Ca exchange Increased intracellular Ca and contractility ```
93
Collagen types
Type I: Bone, Skin, Tendon Type II:Cartilage Type III: Reticulin Type IV: Basement membrane "Be (So Totally) Cool, Read Books"
94
Type I collagen
``` Bone Skin Tendon Dentin Fascia Cornea Late wound repair ``` Defective in osteogenesis imperfecta
95
Type II collagen
Cartilage Vitreous body Nucleus pulposus
96
Type III collagen
Reticulin (skin, blood vessels, uterus, fetus, granulation tissue) Defective in Ehlers-Danlos
97
Type IV collagen
Basement membrane Defective in Alport syndrome
98
Collagen synthesis
1) Synthesis (RER): Gly-X-Y 2) Hydroxylation (ER): of proline and lysine (required vit. C) 3) Glocosylation (ER): of hydroxylysine, hydrogen and disulfide bond formation 4) Exocytosis into extracellular space 5) Cleavage: of terminal regions into insoluble tropocollagen 6) Cross-link: Forming fibrils
99
Multiple fractures, blue sclerae, hearing loss, dental imperfections
Osteogenesis imperfecta
100
Congenital nephritis, deafness, and ocular disturbances
Alport syndrome (type IV collagen)
101
Prader-Willi syndrome
Paternal allele not expressed Retardation Hyperphagia/obesity Hypogonadism Hypotonia
102
Angelman syndrome
Maternal allele not expressed Retardation Seizures Ataxia Inappropriate laughter
103
Trinucleotide repeat expansion diseases
Fragile X: (CGG) Friedreich's ataxia: (GAA) Huntington's: (CAG) Myotonic dystrophy: (CTG) "X-Girlfriends First-Aid Helped-Ace My-Test"
104
Autosomal trisomies
21-Downsyndrome 18-Edwards (rocker-bottom feet, small jaw) 13-Patau's (rocket-bottom feet, cleft palate, microophthalmia/cephaly, polydactyly) "Drink at 21, Election at 18, Puberty at 13"
105
Robertsonian translocation
Nonreciprocal chromosomal translocations 13,14,15,21,22 Long arms fuse @ centromere and short arms are lost
106
Cri-du-chat syndrome
Microdeletion of short arm of chr 5 microcephaly, retardation, high-pitched crying/mewing, epicanthal folds, cardiac VSD
107
Williams syndrome
Microdeletion of long arm of chr. 7 ``` Elfin facies Intellectual disability Hypercalcemia (increased vit. D def) Well-developed verbal skills/extreme friendliness Cardiovascular problems ```
108
22q11 deletion syndromes
Aberrant devo of 3rd and 4th branchial pouches ``` Cleft palate Abnormal facies Thymic aplasia Cardiac defects Hypocalcemia ``` "CATCH-22"
109
DiGeorge syndrome
22q11 deletion Thymus Parathyroid Cardiac defects
110
Velocardiofacial syndrome
22q11 deletion Palate Facial Cardiac defects

Evan's Step 1 Prep Material (72 decks)

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