The genetic code Flashcards
State which molecules are involved in protein synthesis and be able to describe their specific roles Explain the relevance of the genetic code Explain why the genetic code must be at least 3 base pairs per codon Explain why the genetic code is degenerate but not ambiguous Explain the relevance of the nonsense codons Describe the chemical mechanisms involved in tRNA charging
What type of code is the genetic code? (3)
Non-overlapping, degenerate, triplet code
Why is the genetic code degenerate?
The genetic code is degenerate because there are many instances in which different codons specify the same amino acid
What is a frameshift and what did it prove? (2)
A frameshift is due to an insertion or deletion of a codon - shifting the code
It proved that the genetic code is read sequentially from a fixed point
How does mRNA decipher the code?
It binds to tRNA molecules which carry the aa
What is the cell free system? (5)
- Cells are broken and centrifuged
- ATP, GTP - protein synthesised
- Add DNase to remove the DNA
- Add purified mRNA - recover polypeptide
- Determine amino acids
What is a nonsense codon? (2)
UAG, UAA, UGA - stop codons
They signal no aa but termination
Is DNA universal?
Mitochondrial DNA is universal
What are the key features of the structure of tRNA? (5)
- 5’ terminal phosphate group
- 7-bp acceptor stem attached to phosphate
- D arm - loop containing dihydrouridine
- Anticodon arm - anticodon
- T(|)C arm -
What is the mechanism for aminacyl-tRNA synthetases?
Amino acid + tRNA + ATP aminoacyl-tRNA + AMP + PPi
What does the ribosome translate?
mRNA
How is mRNA deciphered?
In codons of 3 nucleotides
What is wobble?
Allows many tRNAs to bind to more than 1 codon
