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STEP 1 > Biochem. > Flashcards

Biochem. Flashcards

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1
Q

histones are rich in

A

arginine and lysine

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2
Q

histones are what charge

A

positive because DNA is negative

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3
Q

what makes up histone core

A

H2A, H2B, HC AND H4 X2

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4
Q

histones are created in what cell cycle phase

A

S phase

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5
Q

what nucleotides are methylated in DNA methylation

A

cytosine and adenine

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6
Q

how do mismatch repair enzymes distinguish between old and new strands in prokaryotes?

A

DNA methylation

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7
Q

deamination of cytosine makes?

A

uracil

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8
Q

what nucleotide has a methyl

A

thymine

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9
Q

3 amino acids required for purine synthesis

A

glycine, aspartate, glutamine

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10
Q

most important difference between purine and pyrimadine synthesis?

A

pyrimadine synthesis requires ATP

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11
Q

What enzyme is deficient in orotic aciduria?

A

UMP synthase - decreases conversion of orotic acid to UMP (thus orotic acid builds up –> orotic aciduria)

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12
Q

Lefluonamide inhibits what enzyme

A

dihydroorotate dehydrogenase

carbamoyl phosphate —> orotic acid

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13
Q

hydroxyurea inhibits what enzyme

A

ribonucleotide reductase

UDP –> dUDP

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14
Q

5 FU inhibits what enzyme

A

thymidylate snythase

dUMP to dTMP

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15
Q

what three drugs inhibit dihydrofolate reductase and in what organisms?

A

MTX –> humans
TMP –> bacteria
pyrimethamine –> protozoa

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16
Q

rate limiting step for pyrimadine synthesis

A

carbamoyl phosphate synthetase 2

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17
Q

what drugs inhibit IMP dehydrogenase?

A

ribavirin and mycophenolate

IMP –> GMP

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18
Q

what drug (s) inhibit PRPP amidotransferase

A 
6 MP (azathioprine)
PRPP--> IMP
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19
Q

adenosine deaminase deficiency

A

buildup of ATP and dATP causes feedback inhibition of ribonucleotide reductase - slows DNA synthesis - decreased synthesis of lymphocytes - SCID

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20
Q

lesch nyhan syndrome inheritance

A

x linked recessive

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21
Q

lesch nyhan syndrome pathogenesis

A

HGPRT deficiency - no recycling of purines - everything is converted into uric acid and increased de novo purine synthesis

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22
Q

telomerase adds genetic material to what end of the chromosome?

A

3’ (always start at 5’)

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23
Q

sickle cell mutation

A

glutamic acid to valine

conservative missense

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24
Q

type of missense mutation that results in an amino acid that is similar in chemical structure as the original amino acid

A

conservative

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25
duchenne muscular dystrophy is what type of mutation?
frameshift
26
defective in XP?
nucleotide excision repair
27
important in repair of spontaneous / toxic deamination?
base excision repair
28
defective in HNPCC?
mismatch repair
29
mutated in ataxia telangiectasia?
nonhomologous end joining
30
mutated in fanconi anemia
nonhomologous end joining
31
Where does energy for DNA/RNA synth (phosphodiesterase bonds) come from?
5' end of incoming nucleotide = triphosphate
32
describe how a phosphodiesterase bond is made
3'OH attacks the incoming 5' triphosphate!!!!
33
3 stop codons
UGA, UAG, UAA
34
What does alpha amantin do and where is it found?
inhibits RNA polymerase II (mRNA synth), found in amanita phalloides - death cap mushrooms causes severe hepatotoxicity if ingested
35
Rifampin MOA
Inhibits RNA polymerase in prokaryotes
36
Actinomycin D MOA
inhibits RNA polymerase in prokaryotes and eukaryotes
37
what is hnRNA
initially transcribed mRNA (mRNA without the processing)
38
what are anti-Smith antibodies and in which disease are they found?
anti-spliceosomal RNPS | found in SLE (highly specific!!!)
39
What are anti-U1 RNA antibodies associated with?
mixed connective tissue disease
40
hsp60 is an example of
chaperone protein - involved in facilitating/maintaining protein folding hsp60 is expressed at high temps to prevent protein denaturing/misfolding
41
is Rb active when phosphorylated or dephosphorylated
dephosphorylated
42
examples of permanent cells (never go to G0)
1) neurons 2) skeletal and cardiac muscle 3) RBCs
43
examples of stable (quiescent) cells
1) hepatocytes | 2) lymphocytes
44
examples of labile cells
1) bone marrow 2) gut epithelium 3) skin 4) hair follicles 5) germ cells
45
secretory cells are rich in what organelle?
RER
46
What are Nissl bodies
RER in neurons (synthesize neurotransmitters)
47
DNA methylation where represses transcription
CpG islands
48
Rate limiting step of purine synthesis
PRPP amidotransferase
49
Where is mRNA synthesized
nucleoplasm
50
Where is tRNA synthesized
nucleoplasm
51
Where is rRNA synthesized
nucleolus
52
5 functions of golgi apparatus
1) glycosylates core proteins to make proteoglycans 2) adds O-oligosaccharide to Serine and Threonine 3) adds N olgiosaccarides to Aspargine 4) adds m6P to lysosomal enzymes 5) adds sulfate to sugars and tyrosine
53
Coarse facial features, clouded corneas, restricted joint movements, high plasma levels of lysosomal enzymes
I cell disease - defect in N-acetylglucosaminyl-1-PHOSPHOTRANSFERASE. No phosphorylation of mannose = low M6P = no targeting of lysosomal enzymes to the lysosome
54
What does a signal recognition particle do
cytosolic ribonucleoprotein that traffics proteins from ribosome to RER
55
What happens if you have absent/deficient signal recognition particle?
buildup of proteins in the cytosol
56
What does a peroxisome break down
1) VLCFA 2) BCFA 3) AA
57
defects in the ubiquitin proteasome system have been implicated in what disease?
parkinsons!
58
synthesis of what occurs in peroxisomes?
plasmalogens - phospholipid found in myelin! No peroxisomes = neurodegenerative disorder.
59
vimentin stains what type of cells
connective tissues - sarcoma
60
desmin stains what type of cells
muscle - rhabdomyosarcoma or leiomyosarcoma
61
cytokeratin stains what type of cells
epithelial cells (keratin) = CA
62
GFAP stains what type of cells
neuroglia | seen in glioblastoma
63
neurofilaments stain what type of cells
neurons (axon) | neuroblastoma
64
nuclear lamins stain what
nuclear envelope and dna within (implicated in progeria)
65
ouabain mOA
inhibits NA-K ATPase by binding to K+ site
66
inheritance of OI
autosomal dominant
67
OI is from a problem with
type I collagen | can't form the triple helix
68
what part of collagen synthesis requires vitamin C?
hydroxylation
69
what part of collagen synthesis requires copper?
lysyl hydroxylase = cross-linking of procollagen (triple helix crosslinking)
70
ATP7A
menkes protein
71
brittle, kinky hair, growth retardation, hypotonia
menkes (copper deficiency)
72
difference between elastin and collagen in terms of structure?
elastin is rich in nonhydroxyylated proline, glycine, and lysine collagen has hydroxylated proline/glycine/lysine
73
what gives elastin its elastic properties
cross-linking
74
southern blot detects what?
dna probe used to detect DNA
75
northern blot detects what?
dna probe to detect rNA
76
western blot detects what?
labelled antibody to identify protein sample
77
southwestern blot detects what?
oligonucleotide probe to detect DNA binding proteins (like transcription factors)
78
constitutive insertion
gene inserted randomly into a genome
79
conditional insertion
gene inserted to a target place in a genome
80
mccune albright snydrome is a problem with what?
G protein signaling
81
unilateral cafe au lait spots polyostotic fibrous dysplasia precocious puberty endocrine abnormalities
mccune albright syndrome
82
example of locus heterogeneity
albinism
83
example of allelic heterogeneity
beta thalassemia
84
using hardy weinberg to calculate x-linked recessive disorders?
``` males = q females = q^2 ```
85
prader willi and angelmans occur because of mutations and deletions on what chromosome
15
86
defects in structural genes are often what type of inheritance?
AD
87
enzyme deficiencies are what type of inheritance?
autosomal recessive
88
What is hypophosphatemic rickets
X linked dominant disorder where there is phosphate wasting in the PCT - resistant to vit. D. Presents like rickets
89
gomori trichrome stain
used to stain ragged red fibers which are part of the mitochondrial myopathies
90
reticulonodular pattern on xray
CF
91
cf is what inheritance and found on what chromosome
AR, found on chr. 7
92
most common cause of death in duchenne muscular dystrophy
dilated cardiomyopathy
93
pathogenesis of myotonic dystrophy
CTG trinucleotide repeat in the DMPK gene - abnormal expression of myotonin protein kinase - causes myotonia, muscle wasting, cataracts, testicular atrophy, balding, arryhtmia (testicles, toupee, ticker, myoTonia)
94
fragile x pathogenesis
CGG trinucleotide expansion in the FMR1 gene on X chromosome | X-tra large testes, jaw, ears
95
CGG repeats
fragile X
96
GAA repeats
Friedrich ataxia
97
CAG repeats
huntington
98
CTG repeats
myotonic dystrophy
99
low AFP, high beta-HCG, low estriol, high inhibin A
trisomy 21
100
low ATP, low beta-HCG, low estriol, low/normal inhibin A
trisomy 18 (edwards)
101
low beta-hCG, low PAPPA, high nuchal translucency
Patau trisomy 13 (downs has high beta-HCG)
102
clenched hands with overlapping fingers
edwards (trisomy 18)
103
clift lip/palate, polydactyly, holoprosencephaly
patau (trisomy 13)
104
what chromosomes can undergo robertsonian translocation
13 14 15 21 22
105
cri du chat is due to what
microdeletion of short arm of chromosome 5 (5p)
106
williams syndrome
deletion of long arm of chr. 7 that contains elastin gene
107
von hippel lindau chromosome number
3
108
renal cell carcinoma chromosome number
3
109
ADPKD with PKD2 defect chromosome number
4
110
huntington chromosome
4
111
cri du chat chromosome
5
112
FAP chromsome
5
113
CF chromosome
7
114
freidreich ataxia chromosome
9
115
wilms tumor chromosome
11
116
wilson disease chromosome
13

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