Translation Flashcards
What is the role of mRNA in translation?
It contains the nucleotide sequence that encodes the protein. (e.g. It is the blueprint for protein building)
What is the role of tRNA in translation?
It delivers a specific amino acid to the ribosome (and peptide chain) by matching its anticodon to the RNA codon.
What is the role of aminoacyl tRNA synthetases in translation?
They are protein enzymes that match the correct amino acid to the tRNA by using the recognition site.
What is the role of a ribosome in translation?
The ribosome is a 2 unit complex that catalyzes the reaction between two amino acids - helping to build a peptide chain.It has three sites: Accepting (A), Peptidyl (P), and Exit (E).
What are the roles of initiation factors in translation?
They are proteins that bring the ribosome to the mRNA and assist in getting the ribosomal machinery assembled.
What are the roles of elongation factors in translation?
They are proteins that deliver tRNAs and move the ribosome down the mRNA.
What are the roles of termination/recycling factors in translation?
They are proteins that end the process at a stop codon and disassociate the subunits so that they can be used again.
What does the genetic code consist of?
64 triplet codons coding for 20 amino acids.
What is the start codon?What amino acid does it encode?
AUGMethionine
What are the general effects of mutations to mRNA?
Because of degeneracy a DNA mutation may have no effect on the resulting protein sequence.OR it could cause a different AA to be encoded changing the resulting peptide sequence + protein function
Describe initiation with regard to translation.
Initiation factors bind. Assemble a ribosome with the start codon AUG and initiator methionine tRNA in the P site ready to receive the next AA tRNA in the A site.
Describe elongation with regard to translation.
A cycle in which AA are added to the polypeptide chain: tRNA enters A site, the, peptide chain from P site attaches to AA from A site. Peptidyl transferase moves the P tRNA to the E, and the A to the P. tRNA in E leaves.Requires 4 ATPs.
Describe termination with regard to translation.
A recycling factor in the A site recognizes a stop codon. This ends elongation and signals to disassociate the ribosomal subunits and release the peptide chain.
Describe recycling with regard to translation.
Recycling is getting the ribosomal subunits ready to be used again in initiation.Apparently this isn’t well understood yet.
What is a missense mutation?
A mutation where the codon is changed thus encoding a different amino acid.
What is a silent mutation?
The codon is changed but the same amino acid is encoded.Perhaps because the mutation was in a wobble position”.”
What is a frame shift mutation?
Addition or deletion of a nucleotide shifts the reading frame for the ribosomal subunits.
What is a nonsense mutation?
A mutation the codes for a premature stop codon.
What is a sense mutation?
A mutation that changes a stop codon into an amino acid codon. Uh oh.
What are the important differences between prokaryotic and eukaryotic initiation with regards to translation?
Bacteria: the ribosome binds right at AUG due to Shine Delgarno sequence. 3 init factors work to assemble full ribosome.Eukaryotes: bind several more init factors including one to the cap. Small subunit scans down mRNA until AUG found, then large subunit joins.
What is cap independent initiation?Who uses it?
Initiation without binding of factors to the cap.Viruses - shut down cap dependent translation in order to hijack a cells machinery.Eukaryotes - when under stress
Explain the significance and effects of mRNA editing.
Such editing is varied depending on the resident tissue, one common effect is the generation of premature stop codons which causes tissue specific protein truncation
Explain the significance and effects of eIF2-alpha phosphorylation.
Phosphorylation of eIF2-alpha shuts down translation. This may be caused by interferon signals or cellular stresses.
Explain the significance and effects of rapamycin treatment.
Rapamycin is a cancer treatment that phosphorylates 4E-BP so that the initiation complex cannot be formed, thus downregulating translation.
