Easy Biochem Flashcards
amino acids in histones
lysine and arginine (positive)
H1
binds to nucleosome and linker DNA to stabilize chromatin fiber
heterochromatin
condensed, methylated, Barr bodies are examples
euchromatin
less condensed, transcriptionally active, sterically accessible
methyaltion
occurs on C and A leading to decrease in transcription
histone actyelation
relaxes coiling, allows fro transcription
amino acids necessary for dna synthesis
GAG
glycine
aspartate
glutamine
characteristics of protomer regions
AT rich (TATA box)
helicase
unwinds DNA
single stranded binding proteins
prevents strand from rejoining
DNA topoismoerases
single stranded nicks to prevent supercoiling
- irinotecan/topotecan = topo 1
- etoposide/teniposide = topo 2
- fluoroquinolones = topo 2 in prokaryotes
primase
makes RNA primer
DNA pol III
only in prokaryotes, 3-5 proofreading
DNA pol I
prokaryote only, degrades RNA primer, replaces with DNA
DNA ligase
joins okazaki fragments
telomerase
eukaryotes only, adds to 3’ end, dysregulated in cancer
silent mutation
amino acid doesn’t change (due to wobble)
missense mutation
one amino acid is changes
nonsense mutation
adds a stop codon (UAG, UAA, UGA)
frameshift mutation
puts sequence out of frame
splice site mutation
keeps intron in that would have been removed
nucleotide excision repair
endonucleases removed bases, DNA pol and ligase fix, occurs in G1
- defective and xeroderma pigmentosa
base excision repair
- glycosylase remove base creating AP site
- AP endonuclease cleaves 5’ end
- lyase cleaves 3’ end
- DNA pol fills gap and ligase seals
- important in spontaneous deamination
mismatch repair
occurs in G2
- defective in Lynch sydnrome
nonhomologous end joining
- for double stranded breaks
- defective in ataxia telangiectasia, BRCA1 and Fanconi aemia
start codon
AUG
stop codons
UAG, UAA, UAG
AATAAA
polyadenylation signal in terminal exon
promoter
site where RNA pol II binds
RNA pol I
makes rRNA, most numberous
RNA pol II
makes mRNA, largest
RNA pol III
makes tRNA, smallest
alpha amanitin
in mushroom caps, inhibits RNA pol II
rifampin inhibits DAN dependent RNA polymerase
inhibits DNA dependent RNA polymerase in prokaryotes
mRNA processing by compartment
- heterogeneous nuclear RNA gets 5’ cap, poly A tail and splicing of introns in nucleus
- mRNA is translated in cytosol
- mRNA quality control includes exonuclease, decapping enzymes and microRNAs
snRNPs
used for mRNA splicing
introns vs exons
introns - junk
exons - coding
*abnormal splicing = thalessemia
microRNAs
regulate gene expression by targeting 3’ untranslated region for degradation
- implicated in cancer