Question 1

Which enzyme is responsible for catalyzing the nucleophilic attack by the 3'-OH group of the primer terminus upon the α-phosphate of the incoming dNTP during DNA replication?

Accepted Answer

DNA polymerase

Question 2

During eukaryotic DNA replication, what is the significance of multiple fixed origins of replication?

Accepted Answer

They enable bidirectional replication and ensure timely duplication of large linear chromosomes.

Question 3

What is the role of topoisomerase during DNA replication?

Accepted Answer

It relieves torsional stress caused by helicase-mediated unwinding of DNA.

Question 4

Which of the following best describes the synthesis of the lagging strand during DNA replication?

Accepted Answer

It is synthesized discontinuously, forming short fragments called Okazaki fragments.

Question 5

Which enzyme is responsible for removing RNA primers and replacing them with DNA nucleotides during DNA replication?

Accepted Answer

DNA polymerase I

Question 6

What is the function of the TATA box in eukaryotic transcription?

Accepted Answer

It serves as a binding site for transcription factors and helps initiate transcription.

Question 7

Which of the following statements about histone acetylation is correct?

Accepted Answer

Acetylation neutralizes lysine residues, weakening histone-DNA interactions and promoting transcription.

Question 8

Which RNA polymerase is primarily responsible for transcribing protein-coding genes in eukaryotes?

Accepted Answer

RNA polymerase II

Question 9

What is the role of the poly(A) tail added to eukaryotic mRNA during posttranscriptional processing?

Accepted Answer

It increases mRNA stability and half-life.

Question 10

Which process allows a single gene to produce multiple protein products in eukaryotes?

Accepted Answer

Alternative splicing

Question 11

During translation, what is the direction in which mRNA is read by the ribosome?

Accepted Answer

5' to 3'

Question 12

Which codon serves as the start codon for translation in eukaryotes, and what amino acid does it encode?

Accepted Answer

AUG, methionine

Question 13

What is the function of aminoacyl-tRNA synthetase in protein synthesis?

Accepted Answer

It attaches amino acids to their corresponding tRNAs using ATP.

Question 14

Which of the following correctly matches the ribosomal subunits of eukaryotes and prokaryotes?

Accepted Answer

Eukaryotes: 60S and 40S; Prokaryotes: 50S and 30S

Question 15

In the mechanism of translation, which site on the ribosome does the incoming aminoacyl-tRNA first bind?

Accepted Answer

A site

Question 16

Which of the following is a consequence of DNA methylation in eukaryotes?

Accepted Answer

Permanent gene inactivation and gene imprinting

Question 17

Which protein factor bends DNA by 90° to facilitate transcription initiation in eukaryotes?

Accepted Answer

TBP (TATA box-binding protein)

Question 18

What is the role of small nuclear ribonucleoproteins (snRNPs) in mRNA processing?

Accepted Answer

They aid in the formation of the pre-mRNA loop during splicing.

Question 19

Which of the following equations correctly represents the formation of a phosphodiester bond during DNA synthesis?

Accepted Answer

$$\mathrm{(dNMP)_{n}} + \mathrm{dNTP} \xrightarrow{DNA\ polymerase} \mathrm{(dNMP)_{n+1}} + PP_i$$

Question 20

A mutation prevents the addition of a 7-methylguanosine cap to pre-mRNA in a eukaryotic cell. Which process would be most directly affected?

Accepted Answer

Translation initiation

DNA Replication, Transcription, and Translation in Eukaryotes: Key Concepts and Mechanisms

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