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Flashcards in translation Deck (27)
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1
Q

What is the role of mRNA in translation?

A

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

2
Q

What is the role of tRNA in translation?

A

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

3
Q

What is the role of aminoacyl tRNA synthetases in translation?

A

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

4
Q

What is the role of a ribosome in translation?

A

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).

5
Q

What are the roles of initiation factors in translation?

A

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

6
Q

What are the roles of elongation factors in translation?

A

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

7
Q

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

A

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

8
Q

What does the genetic code consist of?

A

64 triplet codons coding for 20 amino acids.

9
Q

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

A

AUGMethionine

10
Q

What are the general effects of mutations to mRNA?

A

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

11
Q

Describe initiation with regard to translation.

A

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.

12
Q

Describe elongation with regard to translation.

A

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.

13
Q

Describe termination with regard to translation.

A

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.

14
Q

Describe recycling with regard to translation.

A

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

15
Q

What is a missense mutation?

A

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

16
Q

What is a silent mutation?

A

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

17
Q

What is a frame shift mutation?

A

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

18
Q

What is a nonsense mutation?

A

A mutation the codes for a premature stop codon.

19
Q

What is a sense mutation?

A

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

20
Q

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

A

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.

21
Q

What is cap independent initiation?Who uses it?

A

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

22
Q

Explain the significance and effects of mRNA editing.

A

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

23
Q

Explain the significance and effects of eIF2-alpha phosphorylation.

A

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

24
Q

Explain the significance and effects of rapamycin treatment.

A

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

25
Q

How do antibiotics target translation?

A

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

26
Q

What are the main classes of antibiotics?

A

AminoglycosidesMacrolidesTetracyclinesOthers (real specific, right?)

27
Q

How can intercellular levels of iron be regulated by translation?

A

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.