transcription Flashcards
nucleolus=
- has rna
- dense
- site of rrna synth
- resistant to a amanitin
- pol a found here
nucleoplasm
- poly b found here
- mrna function
- sensitive to a amanitin
pol c
found in nucleoplasm
- sensitive to a amanitin
- does tnra
a amanitin
- mushroom
- poly a is not inhibited so can make rrna
- if low dose then poly c is also made but no b
rrna
- most abundant form
- prokarya has 2-10 copies
- 100 + in eukarya
- prokarya trim this
trna
less copies
- once made, can be creaves with rnase, methylation or OH in prokary
- euk: only diff is that it is processed in nucleus
mrna
- one copy per chromosome
- usually degraded by rnase
- if MRNA: then poly a tail added, 5’ gtp cap
- many proteins prevent it from degradation with “loops” of dna
primary transcript of ANY rna is called
heterogenous nucleopolasmic rna
- found in nuc
- hnRNA
- can give rise to lots of rnas
introns
- cut out loops of dna not in mrna BUT present in hnRNA
- spliceosome: cut by small nuclear rna
genetic code
1) degenerate: more than one codon for AA
2) unambiguous: AA has specific codon
3) universal
trna and aminoacyl
trna + AA –> aminoacyl + Rna
- enzyme is aminoacyl tnra synthetase, specific to each aa
trna structure for transcription
- all end with adenine 3’
- regions with double strand and anticodon
amino acylation reaction
enzyme + AA + ATP –> complex
complex + Trna –> AA-trna + amp + enzyme
wobble hypothesis
- trna have inosine in 5’ position
- inosine can bond to u, a or c so it can read three codons
- this adds to degeneracy
prokaryotic ribosome
- 70 s
- split to 50 + 30
50: made of 5s + 23s + 34 proteins
30 s; made of 16s and 21 proteins
eukaryotic ribosome
80 s
60 s: 7s rna + 28s + 50-60 proteins
40 s: 18s + 25-30 proteins
initiation
n-formyl met is always starting AA
first met is added to trna using thfa
- then 30s binds, then n formly, then 50s and gtp is used up
elongation
- p side for peptide
- a site for amino
- then peptidyl transferase uses gtp to move the holoenzyme from a to p site and make bond
- as protein is made, chaperone helps it fold
end of translation
- falls off at termination godon (uag stugg)
- can be translated at same time by lots of proteins called polysome
post translational proessing
- golgi
- cleave off n formyl met
- form disulfide bonds
- add cofactors or prosthetic groups
- modify any AA
- signal sequence cut off (hydrophobic AA)
protein degradation
- ubiquitin marks it for bad protein
lac operon
- repressor region where protein is made
- region which is promoter
- operator region where repressor binds
- then also lactase permease acetylase which makes mebrane permeable??!
- on when lactose is there so repressor falls off
cyclic amp and lac operon
- when glucose and lactose, then lac operon is off
- if camp, then it binds to catabolite gene acticator (CAP) which binds to promoter and make gene
his operon
- histadine is on, then when his present, it turns off since already have his
selective gene expression
- only some genes are expressed with same dna in kid
histones
made in cyto and transported to nuc
- positive charge to bind neg dna
- rich in lys and arg (+)
- 5-8 types
- no tissue spec
- lots of mods
- long life
nonhistochromatin dna
- both + and - proteins
- short life
- diverse binding to tissues
- less post translational
- fine tune gene expression
liver dna + liver nhc make + THYMUS HISTONE
liver rna
liver dna and thymus nhc make + liver histone
thymus rn
nucleosome
- beans on a string
- open dna not wrapped is transcribed
enhancer
- only in euk
- stim trasncription
- sites separate from promoter (up or down from gene)
zinc finger + leucine zipper
histone with zinc stabilizing ions or leucine
steroids and transcription
- bidn to promote it
- go in cell, nuc then bind to dna to regulate expression
