Topic 4 Flashcards
snRNA
small nuclear RNA
- splicing process in Eukaryotes
miRNA
microRNA
- regulating genes (short pieces)
siRNA
small interfering RNA
- antisense, opposite to normal RNA sequence
RNA polymerase
unwinds DNA & produces RNA transcript from DNA template
- 5’ to 3’
TSS
Transcription Start Site
- +1
- first transcribed base
Promoter
bases preceding the initiation site
- upstream, 5’ direction
Coding bases
downstream of initiation site
- 3’ direction
UTR
Untrnaslated region
- usually on both the 3’ and 5’ ends of most genes
- transcribed but not translated
Consensus promoter sequence
-35 and -10 regions
holoenzyme
RNA polymerase
- 2 alpha + 1 beta + 1 beta’ + 1 sigma subunits
- scans DNA and sigma subunit binds promoter elements to position enzyme
- after binding, sigma unit falls off and remaining subunits form RNA polymerase core enzyme
intrinsic termination
formation of GC-rich hairpin loop followed by 6-8 A’s in template
- only needs the sequence, not any other factor or protein
rho dependent termination
binding of rho hexamer to rut (rho utilization) site, pausing RNA polymerase, rho-mediated dissociation
GTF
general transcription factors
PIC
Pre-initiation complex
- formed by the binding of GTF to promoter and the attraction of RNA poly II complex
TATA box
common promoter sequence at -30bp
- binding site of TATA binding protein (TBP)
CTD
carboxy terminal domain
- protein tail of the beta subunit of RNA poly II
- ends initiation, when phosphorylated by a DTF
- weakens connection of RNA Poly II to other PIC proteins
contranscriptional
translation occurs simultaneously with transcription
conserved sequence
evolutionary relationship between organisms
AAUAAA or AUUAAA
conserved sequence that terminates transcription
- RNA is cleaved 20 bp downstream
5’ capping
7-methylguanosine linked to 5’ end by 3 phosphates (P-P-P-G)
- for protection/stability3
3’ poly-A-tail
polyadenylation
- 150-200 A residues added to 3’ end by poly (A) polymerase (template independent polymerase)
- for stability, protect from RNases
Splicing
introns removed, leaving exons only
-conserved sequences mark splice sites (GU-AG rule)
-occurs by Lariat formation
spliceosomes
includes snRNAs
Degenerate code
64 codons possible, but only 20+ needed, many amino acids have multiple codons
AUG
methionine, start codon
tryptone codon
UGG
reversion
revert mutation back to wild type (@ same mutation site)
suppression
2 mutations cancel each other out (@ different mutation sites)
Stop codons
UAG, UGA, and UAA
amicoacyl-tRNA synthetase
catalyzes charging rxn of tRNA (attachment of aa onto tRNA)
wobble pairing
some tRNA anticodons can pair with multiple codons
- G + U/C
- C + G
- A + C
- U + A/G
- I + U/C/A
Ribosome subunits
Large:
- euk. = 60S
- pro. - 50S
Small:
- euk = 40S
- pro. = 30S
A binding site
amicoacyl
- first site
- binds incoming aa-tRNA
P binding site
peptidyl
- contains growing peptide chain
E binding site
exit
- contains deacylated tRNA
Shine Delgaro sequence
precedes initiation codon
- signals ribosome binding
- pairs with small ribosomal subunit
