Q: Which of the following is a consensus sequence, and what does it represent?

$$5'\text{-}TAYARNA\text{-}3'$$; the most common nucleotide at each position in a set of similar sequences

Question 1

Which of the following best describes the function of the DnaA protein during the initiation of DNA replication in E. coli?

Accepted Answer

It binds to the 9-mer consensus sequences at oriC, bends the DNA, and facilitates the unwinding of the adjacent A-T rich 13-mer regions.

Question 2

Which equation correctly represents the directionality of DNA synthesis by DNA polymerases?

Accepted Answer

$$5' \rightarrow 3'$$

Question 3

A mutation in the gene encoding DnaG in E. coli would most directly affect which process?

Accepted Answer

The synthesis of RNA primers required for DNA polymerase to initiate DNA synthesis

Question 4

Which of the following statements about Okazaki fragments is TRUE?

Accepted Answer

They are short DNA fragments synthesized discontinuously on the lagging strand.

Question 5

Which enzyme is responsible for removing RNA primers and replacing them with DNA nucleotides in E. coli?

Accepted Answer

DNA polymerase I

Question 6

A patient is treated with fluoroquinolone antibiotics. Which enzyme is most likely inhibited, and what is the consequence for bacterial DNA replication?

Accepted Answer

Topoisomerase; supercoiling is not relieved, leading to replication fork stalling

Question 7

Which of the following best explains why telomerase activity is important in stem cells and cancer cells?

Accepted Answer

It prevents the loss of essential genetic information by extending telomeres, allowing unlimited cell division.

Question 8

Which of the following is a consensus sequence, and what does it represent?

Accepted Answer

$$5'	ext{-}TAYARNA	ext{-}3'$$; the most common nucleotide at each position in a set of similar sequences

Question 9

Which of the following best describes the role of the sliding clamp in DNA replication?

Accepted Answer

It increases the processivity of DNA polymerase by holding it onto the DNA template.

Question 10

A eukaryotic cell line is found to have a mutation in the TERT gene. Which of the following outcomes is most likely after several generations?

Accepted Answer

Gradual shortening of telomeres, leading to apoptosis after several generations

Question 11

Which of the following is a key difference between bacterial and eukaryotic DNA replication?

Accepted Answer

Bacteria use DNA polymerase III for leading and lagging strand synthesis, while eukaryotes use multiple DNA polymerases.

Question 12

Which of the following best describes the function of DNA ligase during DNA replication?

Accepted Answer

It joins Okazaki fragments by catalyzing the formation of phosphodiester bonds.

Question 13

Which of the following equations correctly represents the reaction catalyzed by DNA polymerase during nucleotide addition?

Accepted Answer

$$	ext{(dNMP)}_n + 	ext{dNTP} ightarrow 	ext{(dNMP)}_{n+1} + 	ext{PP}_i$$

Question 14

A mutation causes the loss of 3' to 5' exonuclease activity in DNA polymerase III. What is the most likely consequence?

Accepted Answer

Increased rate of mismatched base incorporation during DNA replication

Question 15

Which of the following best describes the role of RNA primers in DNA replication?

Accepted Answer

They provide a free 3' hydroxyl group for DNA polymerase to initiate DNA synthesis.

Question 16

Which of the following is a function of topoisomerase during DNA replication?

Accepted Answer

It relieves supercoiling ahead of the replication fork by cutting and rejoining DNA strands.

Question 17

Which of the following statements about telomerase is TRUE?

Accepted Answer

It is a ribonucleoprotein complex with reverse transcriptase activity.

Question 18

Which class of RNA is directly translated into protein?

Accepted Answer

Messenger RNA (mRNA)

Question 19

Which of the following best describes the pulse-chase experiment that identified mRNA as the genetic messenger?

Accepted Answer

Radioactive uracil was incorporated into RNA, which was then traced moving from the nucleus to the cytoplasm.

DNA Replication and Transcription: Molecular Mechanisms and Regulation

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