Gene Products and Synthesis Flashcards
Features of the genetic code?
Triplets code for a single amino acid
the code is degenerate
A codon is a triplet which are in the same reading frame
What does translation require?
tRNA to link mRNA codons with specific amino acids
Features of tRNA?
Has a clover leaf structure
Has an anticodon on the central loop which are complementary to codons, they are unpaired bases which can hydrogen bond to 1 or someone more codons (wobble pairing)
What allows for wobble pairing?
Only the first 2 bases are important as often they are the same and the 3rd varies therefore the 3rd is less critical and doesn’t need to pair.
What is the shine-Dalgarno sequence?
The 5’ UTR of the mRNA
Prokaryotic translation - initiation?
1) Initiation factors bind to the 30s subunit which binds to mRNA
2) fmet-tRNA in a complex with IF2 enters site
3) 16s rRNA binds to the Shine-Dalgarno sequence in mRNA to align fmet-tRNA with AUG start codon
4) 50s subunit binds to mRNA, accompanied by GTP hydrolysis, releasing GTP+Pi and IF
Prokaryotic translation - elongation?
1) Aminoacyl tRNA binds to elongation factor and enters the site in the ribosome
2) If anticodon of tRNA is complementary to codon then hydrolysis of GTP occurs to the elongation factor which releases GDP+Pi
3) peptidyl transferase process has the protein synthesised
4) translocation of ribosome occurs and tRNA is then discharged from the site
Prokaryotic translation - termination?
1) Stop codon on mRNA presented
2) Release factor enters the site
3) peptide is hydrolysed by the final tRNA
4) Ribosome then disassembles
Where do Transcription and Translation occur in prokaryotes?
Cytoplasm
Where do Transcription and Translation occur in Eukaryotes?
Transcription = nucleus Translation = cytoplasm
Effect on antibiotics on mitochondria?
Slow metabolism and double membrane would initially protect it but long term damage would be caused by protein synthesis and the production of reactive oxygen species
