Q: Which equation best represents the formation of a new phosphodiester bond during DNA chain elongation?

$$\text{(DNA)_n} + \text{dNTP} \rightarrow \text{(DNA)_{n+1}} + \text{PP_i}$$

Question 1

Which property distinguishes DNA polymerase I from DNA polymerase III in E. coli, according to Table 11.2?

Accepted Answer

DNA polymerase I has 5'-3' exonuclease activity, while DNA polymerase III does not.

Question 2

During DNA replication, what is the primary function of DNA gyrase in bacteria?

Accepted Answer

Relieving supercoiling tension generated during unwinding of the DNA helix.

Question 3

Which enzyme is responsible for synthesizing the RNA primer required for DNA polymerase III to begin elongation?

Accepted Answer

Primase

Question 4

Why is DNA synthesis on the lagging strand discontinuous?

Accepted Answer

The lagging strand is synthesized away from the replication fork, requiring multiple primers and short fragments.

Question 5

What is the role of single-stranded binding proteins (SSBPs) during DNA replication?

Accepted Answer

They stabilize the open conformation of the DNA helix by binding to single-stranded DNA.

Question 6

Which equation best represents the formation of a new phosphodiester bond during DNA chain elongation?

Accepted Answer

$$	ext{(DNA)_n} + 	ext{dNTP} ightarrow 	ext{(DNA)_{n+1}} + 	ext{PP_i}$$

Question 7

A mutation disables the 3'-5' exonuclease activity of DNA polymerase III. What is the most likely consequence?

Accepted Answer

The frequency of replication errors will increase due to loss of proofreading.

Question 8

Which step in bacterial DNA replication is analogous to the untwisting of a phone cord, as shown in the image?

Accepted Answer

Relieving supercoiling by DNA gyrase.

Question 9

In eukaryotic cells, what is the function of telomerase during DNA replication?

Accepted Answer

It adds repetitive DNA sequences to chromosome ends to prevent loss of genetic information.

Question 10

Which of the following best describes the process of homologous recombination during DNA replication?

Accepted Answer

Exchange of genetic material between two chromosomes at equivalent positions with substantial sequence homology.

Question 11

A patient’s somatic cells show unusually short telomeres and no detectable telomerase activity. Which condition is most likely associated with this finding?

Accepted Answer

Accelerated cellular aging and reduced cell lifespan.

Question 12

Which enzyme catalyzes the formation of phosphodiester bonds to seal nicks between Okazaki fragments?

Accepted Answer

DNA ligase

Question 13

Why do eukaryotic chromosomes require multiple origins of replication (ORIs)?

Accepted Answer

To facilitate rapid synthesis of large quantities of DNA.

Question 14

Which of the following is a universal phenomenon in DNA replication across bacteria, viruses, and eukaryotes?

Accepted Answer

RNA priming for initiation of DNA synthesis.

Question 15

If DNA polymerase I is inhibited in E. coli, which process will be directly affected?

Accepted Answer

Removal of RNA primers from Okazaki fragments.

Question 16

Which equation represents the directionality of DNA synthesis by DNA polymerase III?

Accepted Answer

$$	ext{DNA synthesis occurs in the 5' ightarrow 3'}$$ direction

Question 17

Which bacterial DNA polymerase is the primary enzyme responsible for DNA replication?

Accepted Answer

DNA polymerase III

Question 18

What is the main function of DNA polymerases IV and V in E. coli?

Accepted Answer

DNA repair and damage tolerance, especially from UV light.

Question 19

Which step in DNA replication is directly responsible for ensuring the fidelity of genetic information?

Accepted Answer

Proofreading by DNA polymerase exonuclease activity.

Question 20

A cell is observed to have active telomerase and maintains telomere length indefinitely. Which cell type is most likely being observed?

Accepted Answer

Stem cell or malignant/cancer cell

DNA Replication and Recombination: Key Concepts and Mechanisms

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