Gene Expression Flashcards
Where does transcription and translation occur in prokaryotes?
together in the cytoplasm
Where does transcription and translation occur in the eukaryotes?
transcription - nucleus, translation - cytoplasm
What is transcription and the steps of the process?
DNA to mRNA
1. initiation
2. elongation
3. termination
What happens in initiation (transcription)?
- euk. require transcription factors before RNAP can bind
- RNA polymerase binds to promoter (contains TATA in euks.) separate strands and begins synthesis
- +1 transcription start point; downstream (right) +, upstream (left) -
forms transcription initiation complex
What happens in elongation (transcription)?
no primer is needed
reads DNA 3’ to 5’; builds mRNA 5’ to 3’
RNAP zips up DNA as it goes
What is termination (transcription)?
reads a transcription terminate site and stops (cleaved by ribonuclease)
euks. - 5’ G cap and poly A tail 3’
What happens after transcription but before translation?
mRNA goes through RNA splicing
introns (used to exit nucleus) are split by spliceosome and turned into exons
goes into cytoplasm
what is translation?
mRNA makes protein
What is the relationship between anticodon and tRNA?
anticodon carried by tRNA covalently bonded to an amino acid is done by aminocacyl - tRNA synthase
What is a codon and examples of it?
codon is on the mRNA
start codon - AUG (pro. fMET, euk. MET)
stop codon - UAA, UAG, UGA
What are the steps of the translation?
initiation
elongation
termination
What happens in initiation (translation)
small subunit binds to mRNA - tRNA pairs - large subunits binds with initiation factors
tRNA in p-site
forms translation initiation complex
what happens in elongation in translation?
A-site: anticodon pairs with codon
P-site: amino acid in A site and carboxyl in P site forms a peptide bond (peptidyl transferase)
E site: tRNA p-site is removed
What occurs in termination (translation)
stop codon is found
release factor binds to A site
- no stop anticodon/tRNA amino acid
translation initiation complex dissocates using GTO
How does RNA and proteins read?
5’ to 3’
N’ to C’ (amino to carboxyl)
