Molecular biochem Flashcards
nucleasome core
(H2A, H2B, H3, H4) x 2
heterochromatin
highly condensed
DNA methylation
- what is methylated
- what does it do
- CpG islands?
- cytosine and adenine
- marks old strands
- if methylated –> mutes transcription
histone methylation
usually represses transcription … sometimes activates
histone acetylation
relaxes DNA coiling –> allows transcription
what adds sugar and phosphate to bases?
PRPP synthetase
leflunomide inhibits?
dihydroorotate dehydrogenase –> therefore inhibits de novo pyrimidine synthesis
mycophenolate and ribavirin inhibit?
IMP dehydrogenase –> inhibits GMP synthesis during de novo purine synthesis
hydroxyurea inhibits?
ribonucleotide reductase –> screws up de novo pyrimidine synthesis
6-mercaptopurine (6-MP) inhibits?
de novo purine synthesis … stops it right at the beginning
5-fluorouracil (5-FU) inhibits?
thymidylate synthase –> decreases dTMP formation –> inhibits de novo pyrimidine synthesis
MTX, TMP, pyrimethamine inhibit what?
Dihydrofolate reductase –> decreases DHF conversion to THF which is needed for dTMP formation
Lesch Nyhan Syndrome
- cause
- sxs
- tx
- HGPRT def in the purine salvage pathway
- Hyperuricemia; Gout; Pissed off (aggressive and self-mutilating); dysTonia
- allopurinol (xanthine oxidase inhibitor)
Adenosine deaminase def
- mechanism
- a/w what condition
can’t shunt adenosine down towards uric acid –> so end up with ATP and dATP excess –> negative feedback that inhibits ribonucleotide reductase –> prevents DNA synthesis
- major cause of AR SCID
DNA polymerase III
- which direction synthesis
- which direction proofread
- 5-> 3 synthesis
- 3–> 5 proofreading exonuclease
DNA polymerase I
degrades RNA primer using 5–>3 exonuclease and replaces it with DNA
missense mutation
NT substitution resulting in a new coded amino acid
nonsense mutation
NT substitution resulting in early stop codon
single strand DNA repair methods (3)
- a/w what conditions?
- NT excision repair (def in xeroderma pigmentosum [pyrimidine dimers])
- base excision repair (imp in repair of toxic/spontaneous deamination)
- mismatch repair (def in HNPCC)
double strand DNA repair method (1)
- what is it mutated in?
nonhomologous end joining (mut in ataxia telengactasia)
how many RNA polymerases do Euks have and what do they do
- 3
- Pol I for rRNA, II for mRNA, III for tRNA
how many RNA polymerases do Prokes have and what do they do
- 1
- makes all 3 kinds of RNA
what end (3 or 5') is AA attached to tRNA - @ what sequence
3’
CCA (can carry aa’s)
Euk ribosomal subunits
40+60 = 80
Prok ribosomal units
30+50 = 70
6-mercaptopurine and 6-thioguanine are converted to their active metabolites by what
hypoxanthine-guanine phosphoribosyl transferase (HGPRT)
what degrades 6-mercaptopurine to inactive metabolite?
xanthine oxidase
what is an irreversible inhibitor of adenosine deaminase?
pentostatin
cytotoxic purine analog
what’s a cytotoxic purine analog that is resistant to degradation by adenosine deaminase?
cladribine
30S unit of Proke ribosome has rRNA strand - what is that piece and its function
16S rRNA
- binds to Shine-Dalgarno sequence
23S rRNA
where is it
what does it do
in 50S subunit
peptidyltransferase function - peptide bond during translation
