Gene expression Flashcards
DNA characteristics
Double stranded thus very stable.
Contains heritable information to be transfered to RNA
RNA
Single stranded thus less stable.
Acts as a messenger of DNA information to be used in protien production
Protien purpose
Carry out cellular functions
Promotor region
Where molecules bind to initate transcription
Transcription
Transfer of DNA information into RNA
Three steps of transcription
- Initiation
- Elongation
- Termination
Transcription - Initiation process
Trasncription factors assemble at TATA site and bind to DNA to cause a kink enabling substances to reach eachother
RNA polymerase role in transcription
Unwinds DNA strands to bring along more transcription factors
Transcription - Elongation process
RNA nucleotides added to template strand from 3 prime
Transcription - Termination process
Once the polyadenylation signal (End signal) is reached, Pre mrna and RNA polymerase is released
Three steps of mrna processing
- Capping
- Tailing
- Splicing
Mrna processing - capping process
Guanine nucleotide is added to 5 prime end of mrna
mrna processing - Tailing
adenine nucelotides are added to 3 prime end of mrna
Purpose of capping and tailing
Facilitate export, stabilise and facilitate ribosome binding in cytoplasm
mrna processing - Splicing
Introns are removed from transcript so exons can join together - occurs in nucleus splicesomes
Exon
Coding region
Intron
Non coding regions in between exons
UTR
Untranslated regions at 5 prime and 3 prime
Splicesomes
Complex of protiens and RNA
Alternate splicing
Different combination of exon joining to form multiple forms of mRNA
Ribosome function and components
Holds tRNA and mRNA to form polypeptides
- Large and small subunit
- E site
- P site
- A site
- Exit tunnel
- mRNA binding site
Transfer RNA
Bring in amino acids via anticodons that bind to codons of mRNA
Translation
mrna exits nucleus into cytoplasm to form polypeptide chains
Translation - Initiation
Small subunit ribosome binds to start site AUG of mrna and binds initiator tRNA via hydrogen bonds followed by bond of Large subunit
Translation - Elongation - Codon recognition
codons are paired with anticodons
Translation - Elongation - Peptide bond formation
Large subunit catalyses peptide bond formations between two adjacent amino acids
Translation - Elongation - Translocation
trna with now lost amino acid sequence is removed from A to P to E site
Translation - Termination
Ribosome reaches stop codon and hydrolosis of P site and trna releases polypeptide
Regulatory protiens
Block translation
Gene expression control
Temporal and spatial control - Protiens are continously produced and cell signalling activates trasncription
Protiens to function in cytoskeleton..
Complete translation on free ribosomes
Protiens that go to endomembrane system…
Complete translation on fixed ribosomes on RER