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Title: Protein synthesis
Description: 1st year university level notes on protein synthesis
Description: 1st year university level notes on protein synthesis
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Outline the mechanism of RNA synthesis in prokaryotic cells
Identify the ways in which eukaryotic transcription differs from
prokaryotic transcription
• Describe the post-transcriptional modifications that occur in eukaryotic
cells during conversion of the primary transcript (heteronuclearRNA or
hnRNA) to mRNA
• Explain the terms exon and intron
• 1944 Avery discovered DNA is the genetic material
• 1953 Crick and Watson determined the DNA structure
• 1957 Crick discovered the central dogma
The central dogma of molecular biology
•
•
Coding properties of nuclei acids
3 sets of experiments defined the relationship between nuclear DNA and protein
expression:
1
...
The genetic code is read in triplets (Crick,1961, Nirenberg,1961, Khorana, 1960’s)
3
...
Initiation
2
...
Termination
E
...
Don't code for any amino acids in mature proteins
Eukaryotic transcription
• More complex --> more proteins involved
o Polymerases
o Initiation factors
o Elongation factors
o Other helper proteins
• Additional mRNA processing
Eukaryotic gene are split
•
mRNA processing
• Capping: formation of 7-methylguanosine cap
at 5’ end
• GTP reacts with 5’ end of mRNA resulting in
addition to 5’ phosphate group (5’ – 5’ bond)
• The guanine is methylated at 7’ position
• Gives RNA stability and attracts ribosome
• S
•
plicing = removal of introduced segments
polyadenylation (many adenines): addition of tail to 3’ end of RNA
• Is a complex process
• Essentially adds 50-250 adenosine residues to the end of the RNA chain
• Added to 3’ end as normal
• In eukaryotes only fully processed mRNA can be exported from the nucleus and is
made available for translation
• Some hnRNAs can be spliced in different ways, resulting in different protein product
from a single gene
Transcription
• All prokaryotic transcription occurs in the cytoplasm
mRNA carries the code for protein production
UTR = untranslated region
Title: Protein synthesis
Description: 1st year university level notes on protein synthesis
Description: 1st year university level notes on protein synthesis