molecular biochem Flashcards
histones
rich in lysine and arginine
positive charge for neg DNA to wrap around
Methylation -> mute
acetylation -> active
heterochromatin
HeterChromatin = Highly Condensed Barr bodies (inactivated X) Darker on EM
Euchromatine
Eu = true = truly transcribed
light on EM
Pyrimadines
C-U-T the py
purines
pure As Gold
which nucleotide has a mehtyl
Thymine
which nucleotide bond is stronger
G-C
which aa are necessary fro purine synthesis?
GAG
glycine
aspartate
glutamine
NucleoSide
base + deoxyribose (Sugar)
NucleoTide
nucleoside + phosphaTe
leflunomide
inhibits dihydroorotate dehydrogenase
cannot make ortic acid from carbamoyl phosphate and aspartate
therefore cannot make pyrimadines
mycophenolate and ribavirin
inhibit IMP dehydrogenase
cannot make GMP from IMP
hydroxyurea
inhibits ribonucloside reductase
cannot make dUMP from UDP
therefore cannot make dTMP
5-FU
inhibits thymidylate synthase
cannot make dTMP
which drugs inhibits Dihydrofolate reductase
MTX
TMP
pyrimethamine
cannot regenerate THF therefore cannot make dTMP
what step of nucleotide synthesis is imparied in ortic aciduria?
cannot combine ortic acid w/aspartate to make UMP
cannot make pyrimidines
adenosine deaminase deficiency
excess ATP and dATP -> feedback inhibition of DNA synthesis -> decreased lymphocyte counts
major cause of AR SCIDs
Lesch-Nyhan syndrome
defective purine salvage d/t absent HGPRT
excess uric acid production and de novo purine synthesis
x-linked recessive
Tx: allopurinol or febuxostat (2nd line)
HGPRT acroynm
Hyperuricemia Gout Pissed off (aggressive, self-mutilation) Retardation dysTonia
allopurinol and febuoxostat
xanthine oxidase inhibitors cannot make uric acid
probenecid
increases excretion of uric acid in urine
DNA topoisomerase
create a single or double stranded break in helix to add or remover super coils
type II/DNA gyrase and type IV inhibited by fluoroquinolones
DNA polymerase III
prokaryotic only
elongates laggin strand until it reaches primer of preceding fragments
5’-3’ synthesis
3’-5’ proof reading
DNA polymerase I
prokaryotic only
degrades DNA primer and replaces it with DNA
same as III, but ecises RNA primers w/5’-3’ exonuclease
telomerase
RNA-dependent DNA polymerase that adds DNA to 3’ end of chormosomes to avoid loss of genetic material w/duplication
Eukaryotes only
Lac operon
E. coli, increases lactose metabolism when needed
low glucose -> increased AC -> increased cAMP -> activation CAP -> increased transcription
high lactose -> unbinds repressor protein -> increased transcription
nucleotide excision repair
endoneucleases release oligonucelotides w/damaged bases
repairs bulky helix distorting lesions (UV damage)
G1 phase
defective in xeroderm pigmentosum
xeroderma pigmentosum
prevents repair of pyrimidine dimers d/t UV exposure
base excision repair
base-specific glycosylase removes altered base
thru-out cell cycle
important in repair of spontaneous/toxic deamination
mismatch repair
mismatched nucleotides are removed
G2 phase
defective in hereditary non-polyposis colorectal cancer (HNPCC)
nonhomologous end joining
repairs double stranded breaks
some DNA ma be lost
mutated in ataxia telangiectasia and fanconi anemia
DNA/RNA/protein synthesis direction
DNA and RNA are both synthesized 5’ -> 3’
5’ end bares triphosphate (energy for bond)
protein synthesis N->C
mRNA read 5’ -> 3’
mRNA codones
AUG (inAUGurates synthesis)
rarely GUG
in eukaryotes codes for methionine
in prokaryotes codes for fMet
mRNA stop codones
UGA
UAA
UAG
promoter sequence
TATA box
RNA polymerase II binds
mutations usually result in dramatic decrease in gene transcription
RNA polymerase I
makes rRNA (most numerous/Rampant)
RNA polymerase II
makes mRNA (largest/massive) opens DNA at promoter site
RNA polymerase III
makes tRNA (smallest/tiny)
RNA polymerases
do not have proof reading ability
prokaryotes have 1 polymerase w/all 3 fnxs
alpha-amanitin
found in amansita phalloides (death cap mushrooms)
inhibits RNA polymerase -> severe hepatotoxcity
rifampin
inhibits prokaryote RNA polymerase
actinomycin D
inhibits RNA polymerases in both prokaryotes and eukaryotes
RNA processing in eukaryotes
initial transcript is hnRNA which is modified:
- capping of 5’ end
- polyadenylation of 3’
- splicing of introns
- > mRNA -> transported into cyto for translation
anti-snRNPs
aka Smith Abs
SLE
anti-U1 RNP abs
mixed CT disease
tRNA structrue
cloverleaf form
anti-codon end opposite 3/ aminoacyl end
CCA at 3’ end (Can Carry Aa)
charging of tRNA
aminoacyl-tRNA synthetase checks to make sure matchis correct
wobble
accuracy only required for first two base-pairs
protein synthesis initiation
initiated by GTP hyrolysis, initiation factors help assemble 40s, released when 60s binds
elongation
aminoacyl-tRNA binds to site A
rRNA catalyzes peptide bond
riboseoms advances 3 nucleotides toward 3’ end of mRNA
