Biochem Flashcards
Euchromatin vs heterochromatin
Euchromatin- transcribed (“truly transcribed”)
heterochromatin- condensed, transcriptionally active
What amino acids are histones rich in?
lysine and arginine- pos charged
What histone is not part of the nucleosome
H1
Histone methylation vs acetylation
Methylation- represses DAN transcription (“Mute”)
Acetylation- relaxes coiling, allowing for transcription (“Active”)
What are purines vs pyrimidnes?
Purines: A, G (2 rings)
Pyrimidines: C, T, U (1 ring)
What amino acids are necessary for purine synthesis?
GAG
Glycine
Aspartate
Glutamine
Which pathway is orotic acid involved in?
Pyrimidine base production
What pathways are carbamoyl phosphate involved in?
de novo pyrimidine synthesis
urea cycle
What does Leflunomide inhibit
dihydroorotate reductase (mitochondrial, pyrimidine)
What does mecophenolate inhibit?
IMP dehydrogenase (Purine-GMP prod)
What does ribavirin inhibit?
IMP dehdrogenase (purine-GMP prod)
What does hydroxyurea inhibit?
ribonucleotide reductase (UDP to dUDP)
What do 6-MP and azathioprine inhibit?
de novo purine synthesis
Adenoside deaminase deficiency
SCID
excess ATP and dATP
Hyperuricemia, gout, self-mutilation
Lesch-Nyhan
HGPRT (hypoxanthine to IMP, guanine to GMP)
Describe purine salvage?
GMP-Gunanine-Xanthine-Uric acid
AMP-IMP-Hypoxanthine-Xanthine-Uric acid
DNA pol I vs DNA pol III
DNA pol III- elongates leading and lagging strand (5’-3’ synth), proofreads with 3’-5’ exonuclease
DNA pol I- degrades RNA primer, replaces with DNA
What is a transition and transversion mutation?
Transition- purine to purine or pyrimidine to pyrimidine
Transversion- purine to pyrimidine etc
What is mutated in ataxia tenagiectasia?
repair of double stranded breaks
When is nucleotide excision repair vs base excision repair used?
nucleotide excision repair- bulky distortion (eg pyrimidine dimer)- done by specific endonucleases
base excision repair- altered base (eg deamination)
What enzymes are involved in base excision repair
Glycosylase removes base AP-endonuclease cleaves 5' end Lyase cleaves 3' end DNA polymerase b fins gape ligase seals
How are DNA, RNA and protein synthesized?
DNA, RNA: 5’-3’
Protein- N to C terminus
What do the RNA polymerases do?
RNA pol I: makes rRNA
RNA pol II: makes mRNA (opens DNA at promoter site
RNA pol III: makes tRNA
a-amanitin toxicity
inhibits RNA pol II
severe hepatotoxicity