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 the entire chromosome is replicated efficiently.

Question 3

What is the role of topoisomerase during DNA replication?

Accepted Answer

It relieves torsional stress caused by DNA unwinding.

Question 4

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

Accepted Answer

It is synthesized discontinuously, forming Okazaki fragments.

Question 5

What is the function of primase during DNA replication?

Accepted Answer

It synthesizes short RNA primers to provide a starting point for DNA polymerase.

Question 6

Which DNA polymerase activity is responsible for removing RNA primers and replacing them with DNA nucleotides during nick translation?

Accepted Answer

DNA polymerase I exonuclease and polymerase activities

Question 7

In eukaryotic transcription, which polymerase is responsible for synthesizing mRNA from protein-coding genes?

Accepted Answer

RNA polymerase II

Question 8

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

Accepted Answer

It is the eukaryotic counterpart to the bacterial -10 region and helps initiate transcription.

Question 9

Which modification to histones is associated with increased transcriptional activity?

Accepted Answer

Acetylation of lysine residues

Question 10

What is the consequence of neutralizing the basic lysine residues in histones via acetylation?

Accepted Answer

It weakens the ionic interactions between histones and DNA, facilitating transcription.

Question 11

During posttranscriptional processing in eukaryotes, what is the purpose of adding a 7-methylguanosine cap to the 5' end of pre-mRNA?

Accepted Answer

To facilitate ribosome binding and protect mRNA from degradation

Question 12

Which complex is responsible for the splicing of pre-mRNA in eukaryotic cells?

Accepted Answer

Spliceosome

Question 13

Alternative splicing allows one gene to:

Accepted Answer

Specify multiple proteins by generating different mRNA variants.

Question 14

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

Accepted Answer

5' to 3'

Question 15

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

Accepted Answer

It attaches the correct amino acid to its corresponding tRNA.

Question 16

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

Accepted Answer

AUG, which encodes methionine

Question 17

What is the composition of the eukaryotic ribosome in terms of its subunits?

Accepted Answer

60S and 40S

Question 18

During bacterial translation initiation, what is the correct sequence of events?

Accepted Answer

Initiation factors IF1 and IF3 dissociate the 70S ribosome, mRNA and initiator tRNA bind the 30S subunit, then the 50S subunit joins.

Question 19

Which process is directly responsible for the heritable silencing of one X chromosome in female mammals?

Accepted Answer

DNA methylation of CpG islands

Question 20

A mutation in the gene encoding DNA methyltransferase 1 (DNMT1) would most likely affect which cellular process?

Accepted Answer

Maintenance of DNA methylation patterns during cell division

DNA Replication, Transcription, and Translation: Key Mechanisms in Molecular Biology

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