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Genetics Lecture > Translation Elongation and Termination > Flashcards

Translation Elongation and Termination Flashcards

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1
Q

What are the first two steps for the starting condition in elongation?

A

The small and large subunits come together to form a ribosome
The mRNA is bound to the small subunit and the start codon is positioned next to the P site

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2
Q

What are the 3rd and 4th steps for the starting of elongation?

A

The initiator tRNA is located in the P site and is paired with the start codon. The first amino acid in the polypeptide is the amino acid at the N terminus.
The second codon is positioned next to the A site, and the A site is empty

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3
Q

What are the steps in each cycle for elongation?

A
  1. Entry of an aminoacyl-tRNA into the A site
  2. Peptide bond formation
  3. Translocation
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4
Q

What are the three different proteins required for elongation?

A

eEF1 Alpha
eEF1 Beta Gamma
eEf2

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5
Q

What is the 1st step of an elongation cycle?

A

The attachment of an aminoacyl-tRNA to the A site of the ribosome

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6
Q

What is the attachment of an aminoacyl-tRNA to the A site of the ribosome aided by?

A

eEF1 Alpha and eEf1 Beta Gamma

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7
Q

How does aminoacyl-tRNA enter the A site?

A

It enters in such as way that allows pairing between its anticodon and the second codon

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8
Q

What will the amino acid attached to the aminoacyl-tRNA become?

A

It will become the second amino acid in the polypeptide

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9
Q

What is the 2nd step in the elongation cycle?

A

A peptide bond is formed between the methionine in the P site and the amino acid in the A site

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10
Q

What occurs simultaneously as a peptide bond is formed between the P and A site?

A

The covalent bond linking the methionine to the tRNA in the P site is broken
The tRNA in the P site is now empty

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11
Q

When the P site is empty, what happens to the aminoacyl-tRNA in the A site?

A

It is now linked to two amino acids
The tRNA is attached to the polypeptide and is now called the peptidyl-tRNA

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12
Q

What enzyme catalyzes the peptide bond formation and transfer of amino acids to the peptidyl-tRNA?

A

Peptidyl transferase

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13
Q

Where is peptidyl transferase located?

A

In the large subunit
It is the 28S rRNA

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14
Q

What is the 3rd step in elongation?

A

Translocation

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15
Q

What eEF is required for translocation?

A

eEF2

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16
Q

What happens to the ribosome during translocation?

A

The ribosome shifts its position slightly in relation to the mRNA
The star codon, which was next to the P site, is now next to the E site, and codon 2, which was next to the A site, is now next to the P site, and codon 3 is now positioned next to the A site
(BASICALLY EVERYTHING MOVES ONE SPACE)

17
Q

What happens to tRNAs during translocation?

A

The empty tRNA is shifted from the P site to the E site, the peptidyl-tRNA is shifted from the A site to the P site, and the A site is now open for another aminoacyl-tRNA to enter.
The cycle can then repeat itself.
(once again, everything moves one)

18
Q

In termination, what are the stop codons?

A

Stop codons are translation termination signals
The codons are UGA, UAA, or UAG

19
Q

When does termination begin?

A

When one of the three stop codons is positioned adjacent to the A site of the ribosome

20
Q

True/False, there is only one stop codon present in mRNA.

A

True
It is the first UGA, UAA, or UAG encountered by the ribosome as it moves along the mRNA

21
Q

What base sequence lies beyond the stop codon?

A

3’ UTR

22
Q

What protein does termination of translation require? What does it do?

A

eRF1
eRF1 can attach to any one of the three stop codons

23
Q

What happens when a stop codon is positioned next to the A site?

A

The stop codon is recognized by eRF1, attaching to the stop codon

24
Q

What does eRF1 interact with? What does it cause?

A

eRF1 interacts with the peptidyl transferase of the ribosome, causing the peptidyl transferase to cleave the bond between the peptidyl tRNA and the polypeptide

25
Q

What is the result of the cleaved bond between the peptidyl tRNA and the polypeptide?

A

It results in the release of the polypeptide from the tRNA and detachment of the polypeptide and the empty tRNA from the ribosome

26
Q

What happens at the end of the translation process?

A

eRF1, the small and large subunits, and the mRNA all detach from one another

Genetics Lecture (17 decks)

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