translation

Question 1

What is the role of mRNA in translation?

Answer 1

It contains the nucleotide sequence that encodes the protein. (e.g. It is the blueprint for protein building)

Question 2

What is the role of tRNA in translation?

Answer 2

It delivers a specific amino acid to the ribosome (and peptide chain) by matching its anticodon to the RNA codon.

Question 3

What is the role of aminoacyl tRNA synthetases in translation?

Answer 3

They are protein enzymes that match the correct amino acid to the tRNA by using the recognition site.

Question 4

What is the role of a ribosome in translation?

Answer 4

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).

Question 5

What are the roles of initiation factors in translation?

Answer 5

They are proteins that bring the ribosome to the mRNA and assist in getting the ribosomal machinery assembled.

Question 6

What are the roles of elongation factors in translation?

Answer 6

They are proteins that deliver tRNAs and move the ribosome down the mRNA.

Question 7

What are the roles of termination/recycling factors in translation?

Answer 7

They are proteins that end the process at a stop codon and disassociate the subunits so that they can be used again.

Question 8

What does the genetic code consist of?

Answer 8

64 triplet codons coding for 20 amino acids.

Question 9

What is the start codon?What amino acid does it encode?

Answer 9

AUGMethionine

Question 10

What are the general effects of mutations to mRNA?

Answer 10

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

Question 11

Describe initiation with regard to translation.

Answer 11

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.

Question 12

Describe elongation with regard to translation.

Answer 12

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.

Question 13

Describe termination with regard to translation.

Answer 13

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.

Question 14

Describe recycling with regard to translation.

Answer 14

Recycling is getting the ribosomal subunits ready to be used again in initiation.Apparently this isn’t well understood yet.

Question 15

What is a missense mutation?

Answer 15

A mutation where the codon is changed thus encoding a different amino acid.

Question 16

What is a silent mutation?

Answer 16

The codon is changed but the same amino acid is encoded.Perhaps because the mutation was in a wobble position”.”

Question 17

What is a frame shift mutation?

Answer 17

Addition or deletion of a nucleotide shifts the reading frame for the ribosomal subunits.

Question 18

What is a nonsense mutation?

Answer 18

A mutation the codes for a premature stop codon.

Question 19

What is a sense mutation?

Answer 19

A mutation that changes a stop codon into an amino acid codon. Uh oh.

Question 20

What are the important differences between prokaryotic and eukaryotic initiation with regards to translation?

Answer 20

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.

Question 21

What is cap independent initiation?Who uses it?

Answer 21

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

Question 22

Explain the significance and effects of mRNA editing.

Answer 22

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

Question 23

Explain the significance and effects of eIF2-alpha phosphorylation.

Answer 23

Phosphorylation of eIF2-alpha shuts down translation. This may be caused by interferon signals or cellular stresses.

Question 24

Explain the significance and effects of rapamycin treatment.

Answer 24

Rapamycin is a cancer treatment that phosphorylates 4E-BP so that the initiation complex cannot be formed, thus downregulating translation.

Question 25

How do antibiotics target translation?

Answer 25

Antibiotics inhibit translation by interfering with ribosome through tRNA binding, elongation, and peptidyl transferase.Antibiotics often confer a subtle confirmation change - shutting down translation.

Question 26

What are the main classes of antibiotics?

Answer 26

AminoglycosidesMacrolidesTetracyclinesOthers (real specific, right?)

Question 27

How can intercellular levels of iron be regulated by translation?

Answer 27

Low iron = Iron Response element BP binds to transferrin receptor protecting mRNA from degradation = higher synthesis of transferrin.High iron = IRE BP can no longer bind IRE so transferrin mRNA is degraded.