Translation Flashcards
(27 cards)
Translation
-the production of a polypeptide
based on the codon sequence of an mRNA.
-is coupled with transcription in prokaryotic cells
-occurs in the cytoplasm, after nuclear transcription of mRNA,
in eukaryotic cells
The coupling of transcription and translation is present in:
Prokaryotes
Multiple
polypeptides can
be translated
from one mRNA
at once in:
both prokaryotes and eukaryotes
Two significant regions of a tRNA molecule:
Anticodon and amino acid (3’ end)
What does each ribosomal site hold?
A
P
E
A: aminoacyl tRNA
P: the tRNA with growing polypeptide attached
E: a tRNA that will exit
Shine Delegrano Sequence
In prokaryotes, location where ribosomes bind to initiate translation. 7-8 units from AUG
The Initiation of Translation in bacteria
- Small subunit and initiator tRNA bind to the 5’ end of the mRNA.
- Scanning begins to find the correct AUG start codon(euks).
- Large subunit binds to the small subunit.
Put the following events of bacterial transcription in
chronological order.
1. Sigma binds to the promoter region.
2. The double helix of DNA is unwound, breaking hydrogen
bonds between complementary strands.
3. Sigma binds to RNA polymerase.
4. Sigma is released.
5. Transcription begins.
1,3,2,5,4
Where is the start codon located?
Immediately downstream of the 5’ UTR.
Elongation of Translation
- Charged tRNA enters at the A site of the ribosome.
- A peptide bond is created between the amino acids in the A and P sites
- The bond is broken between tRNA-a.a. in the P site
- The ribosome translocates toward the 3’ end of the mRNA
Wobble Rules
U -> A, G
G-> U, C
Where does translation occur?
ribosomes
Polyribosome
a messenger rna molecule that is being translated by two or more ribosomes.
transfer RNA
an RNA molecule with an anticodon at one end and an amino acid at the other. Each carries a specific amino acid and binds to the corresponding codon in messenger RNA during translation.
aminoacyl tRNA
tRNA with an amino acid attached.
aminoacyl tRNA synthetases
catlyze the addition of amino acids to tRNA
Protein Synthesis
- An aminoacyl tRNA diffuses into the A site: if it’s anticodon matches a odon in mRNA, it stays in the ribosome.
- A peptide bond forms between the amino acid held by the aminoacyl tRNA in the A site and the growing polypeptide, which was held by a tRNA in the P site.
- The ribosome moves relative to the mRNA by one codon, and all three tRNA’s are shifted one position within the ribosome. The tRNa in the E site exits: the tRNA in the A site moves to the P site, The A site is empty and ready for another aminoacyl tRNA.
Protein synthesis starts at the ___ end and ends at the ___ end.
Amino, carboxy.
Peptidyl transferase,
The peptidyl transferase activity of the ribosome catalyzes peptide bond formation between the adjacent amino acids.
How can 61 codons be translated with only 40 tRNAs?
wobbling
In bacteria, what does the initiator tRNA code for?
F-Methionine
Initiation differences prok vs euk:
Prok: F-Met
Euk: several initiators, ribosome first associates with 5’ cap, and initiator carries normal methionine.
What does translocation require?
type of protein, elongation factor.
How does translation termination occur?
When the translocating ribosome reaches one of the stop codons (UAA, UAG, UGA), a protein called release factor recognizes the stop codon and fills the A site
