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unit 12 gene expression at the molecular level - Coggle Diagram
unit 12 gene expression at the molecular level
transcription
elongation
uracil substitutes thymine
termination
termination sequence
dissociation of protein and mRNA
initiation
RNA polymerase (II in eukaryotes)
RNA strand synthesized from 5'-3' direction
promoter (sigma factor in prokaryotes)
RNA processing
splicing
uses spliceosomes (snRNP "small nuclear RNA + proteins")
rRNA and tRNA are self splicing
removal of introns and keeping exons
poly A tail
addition of 100-200 adenine neucleotide bases
capping
addition of modified guanosine cap to the 5' end
translation
rRNA makes the ribosomal subunits
P cite: peptidyl cite
E cite: exit cite
A cite: aminoacyl cite
tRNA (transfers amino acids to ribosomes)
aminoacyl tRNA synthesase
uses GTP to create charged tRNA (aminoacyl tRNA)
process
elongation
new aminoacyl tRNA enters A cite
polypeptide removed from the tRNA in P cite and bind to tRNA in A cite
codon anticodon recognition
translocation of ribosome by 1 codon towards 5'-3'
uncharged tRNA exits from E cite
termination
ribosome reaches a stop codon (UAA, UAG, UGA)
stop codon not recognized by tRNA, but by a release factor protein
release factor dissociates ribosome, and hydrolysis bond between the polypeptide and the last tRNA
initiation
guanosine cap at 5' recognized by cap binding protein in eukaryotes
start codon recognized by aminocyl tRNA (AUG)
forms a complex
both enter the ribosome in the p cite
ribosomal binding sequence in prokaryotes
codons
3 base sequence each encodes a specific amino acid
lacation
prokaryotes
transcription and translation happen in the cytosol
no RNA processing
eukaryotes
transcription and processing happen in the nucleus
translation happens in cytosol (free ribosome or ER ribosomes)