Translation 2

• Which ribosomal subunit binds the mRNA and start codon first?

  Small subnit
• Where on the mRNA does this subunit initially bind?

  Shine-Delgarno
• Where is the Shine Dalgarno sequence located and what does it do?

  5' UTR of mRNA. Binding site for small ribosomal
• What part of the small subunit interacts with the Shine Dalgarno sequence, and how do they interact?

  16s rRNA through collision binding
• Which enters the growing initiation complex first: large subunit or initiation tRNA, and at what stage of the process?

  initiator RNA
• What amino acid does the initiator tRNA encode for?

  fMet
• Once the initiation complex is complete, which of the three ribosome functional sites (A, P, or E) is the initiator tRNA located in?

  P site
• How does the collision-recognition approach to prokaryotic initiation complement the common use of operons by bacteria?

  All start codons can be recognized by complex
• What is the role of GTP in translational initiation?

  It provides energy
• Proteins called _____________________s also play a role in helping the components of translation come together appropriately during the initiation process.

  initiation factors
• Which ribosomal subunit binds the mRNA and start codon first?

  Small subunit
• Where on the mRNA does this subunit initially bind?

  5' cap
• Once this subunit is on the mRNA, how does it find the start codon? When it finds a start codon, what determines if the subunit stays there and actually initiated translation at that start codon?


  Scans for the start condon. Presence of Kozak sequences
• Which enters the growing initiation complex first: large subunit or initiation tRNA, and at what stage of the process does it enter?

  initiation tRNA
• What role does the initiator tRNA play in initiation? Was it already part of your answer to “c” above? (your answer to “c” should have two parts involving the Kozak sequence and the start codon).


  initiator tRNA already bound to small subunit.
• What amino acid does the initiator tRNA encode for?

  Methionine
• What is a Kozak sequence, or Kozak context?

  sequences around start codon
• Is the first AUG downstream from the 5’ end usually the actual start site?

  No
• Is the first AUG downstream from the 5’ end ALWAYS the actual start site? If not, explain what about the mRNA could cause that first AUG to be passed over.

  It causes weak kozak sequences
• If the eukaryotic small ribosomal subunit (with its initiator tRNA) loads onto the 5’ cap of the mRNA, how is it possible that the mRNA’s 3’ Poly(A)tail also plays a role in the ability of the small subunit to load onto the mRNA?

  5' and 3' ends come together to form an initation complex
• What is the role of GTP in translational elongation?

  Enables for the tRNAs to be brought into A-site
• Proteins called _____________________s also play a role in helping the components some components come together appropriately during the translational elongation process.

  elongation factors
• When elongation begins, what enters the ribosome A-site?

  Charged tRNA
• What interaction (that is, interaction between what and what) ensures that the correct tRNA enters the A-site and stably binds there?

  Codon and anticodon interaction
• What enzymatic activity in the large subunit is triggered by the arrival of an appropriate charged tRNA in the A-site? ....... a. Does this enzyme cut the amino acid off the A-site tRNA and add it to the P-site tRNA or does it cut the polypeptide off the P-site tRNA and add it to the A-site tRNA?


  Cuts the polypeptide off the P-site tRNA and add into the A-site tRNA
• What kind of bond is formed by this enzyme? (that is, what kind of bond links amino acids within a polypeptide)? (the answer is NOT just “covalent bond”

  peptide bond
• Which terminus of the polypeptide is attached to the tRNA?

  C terminus
• Which terminus of the growing polypeptide extends out of the ribosome into the cytoplasm?

  N terminus
• What two functional groups are bound together to create this bond?

  COOH and NH2 come together CO-NH
• Peptidyl transferase is a ribozyme; what does this mean?


  It has an RNA component + enzyme activity
• The ribosome move in what direction on the mRNA (or “reads” the mRNA in what direction)? That is, it moved from ____’ to ____

  5' to 3'
• . After translocation occurs… a. What will enter the now empty A-site?

  Charged tRNA
• . After translocation occurs… b. What happens to the uncharged t-RNA in the E-site?

  leaves the ribosome
• What is meant by coupling of transcription and translation? Does coupling of transcription and translation occur in prokaryotes? In eukaryotes?

  Coupling means transcription + translation occur at the same time. Only in prokaryotes because mRNA processing in not required