Question 1

Which of the following statements correctly describes the role of the initiator tRNA in translation initiation in prokaryotes?

Accepted Answer

The initiator tRNA is the only aminoacyl-tRNA that can directly enter the partial P site on the small ribosomal subunit.

Question 2

In eukaryotic translation initiation, which factor is responsible for generating the active form of eIF2?

Accepted Answer

eIF2B

Question 3

What is the main difference between the initiator tRNA and the elongator tRNA-Met in eukaryotes?

Accepted Answer

Initiator tRNA has a unique sequence and 3D shape that allows it to bind to initiation factors, while elongator tRNA-Met does not.

Question 4

Which of the following best describes the sequence of events during translation initiation in prokaryotes?

Accepted Answer

The small ribosomal subunit binds to the mRNA first, then the initiator tRNA joins.

Question 5

Which molecule acts as a small GTPase during translation initiation in both prokaryotes and eukaryotes?

Accepted Answer

IF-2/eIF-2

Question 6

During translation initiation in eukaryotes, what is the role of eIF2-GTP?

Accepted Answer

It binds to the initiator tRNA and helps it associate with the small ribosomal subunit.

Question 7

Which of the following is a key difference between translation initiation in prokaryotes and eukaryotes?

Accepted Answer

Eukaryotes use more initiation factors and a different mechanism to find the start codon.

Question 8

Which equation correctly represents the GTP hydrolysis reaction that occurs during translation initiation factor activation?

Accepted Answer

$$\mathrm{GTP} \rightarrow \mathrm{GDP} + \mathrm{P_i}$$

Question 9

A mutation prevents the initiator tRNA from binding to the P site in prokaryotes. What is the most likely consequence?

Accepted Answer

The ribosome will fail to assemble properly, and translation initiation will be blocked.

Question 10

Which of the following statements about IF-2 in prokaryotic translation initiation is correct?

Accepted Answer

IF-2 is a small GTPase that brings the initiator tRNA to the P site.

Question 11

In eukaryotic translation initiation, which complex is responsible for scanning the mRNA to locate the start codon?

Accepted Answer

The 43S preinitiation complex

Question 12

Which of the following best explains why the initiator tRNA is unique compared to other tRNAs?

Accepted Answer

It has a distinct sequence and 3D shape that allows it to interact with initiation factors.

Question 13

Which of the following is true regarding the start codon recognition in eukaryotes?

Accepted Answer

The ribosome scans the mRNA from the 5' cap until it finds the first AUG codon.

Question 14

A researcher adds a non-hydrolyzable GTP analog to a eukaryotic translation initiation reaction. What is the most likely effect?

Accepted Answer

The large ribosomal subunit will fail to bind, stalling initiation.

Question 15

Which of the following is a correct description of the role of eIF2B in eukaryotic translation initiation?

Accepted Answer

eIF2B acts as a guanine nucleotide exchange factor, regenerating eIF2-GTP from eIF2-GDP.

Question 16

Which of the following steps is unique to eukaryotic translation initiation compared to prokaryotic initiation?

Accepted Answer

Scanning of the mRNA by the small ribosomal subunit to locate the start codon.

Question 17

Which of the following is the correct order of events for translation initiation in eukaryotes?

Accepted Answer

Initiator tRNA binds to small subunit, complex binds to mRNA, scanning for start codon, large subunit joins.

Question 18

Which of the following is a consequence of a mutation that prevents eIF2 from binding GTP?

Accepted Answer

Initiator tRNA will not be delivered to the ribosome, blocking translation initiation.

Translation Initiation: Common Features and Differences in Prokaryotes and Eukaryotes

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