Question 1

Which of the following best describes the semiconservative model of DNA replication?

Accepted Answer

Each daughter DNA molecule consists of one parental strand and one newly synthesized strand.

Question 2

The Meselson-Stahl experiment used isotopes of nitrogen to demonstrate the mode of DNA replication. After one round of replication in $$^{14}N$$ medium, what was the density of the DNA observed?

Accepted Answer

Intermediate between $$^{15}N$$ and $$^{14}N$$

Question 3

Which enzyme is responsible for relieving the supercoiling tension ahead of the replication fork during DNA replication in E. coli?

Accepted Answer

DNA gyrase

Question 4

What is the primary function of DNA polymerase I in E. coli during DNA replication?

Accepted Answer

Removal of RNA primers and filling in the resulting gaps with DNA

Question 5

Which of the following statements about Okazaki fragments is correct?

Accepted Answer

They are short DNA fragments synthesized on the lagging strand during DNA replication.

Question 6

In eukaryotic DNA replication, which DNA polymerase is primarily responsible for synthesizing the leading strand?

Accepted Answer

DNA polymerase ε (epsilon)

Question 7

Which of the following is a key reason why eukaryotic DNA replication is more complex than prokaryotic DNA replication?

Accepted Answer

Eukaryotic chromosomes are linear and complexed with nucleosomes.

Question 8

What is the function of the sliding DNA clamp in DNA polymerase III holoenzyme?

Accepted Answer

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

Question 9

Which of the following best explains the genetic basis of aging in humans?

Accepted Answer

Progressive shortening of telomeres with each round of DNA replication in somatic cells.

Question 10

A mutation in the gene encoding single-stranded binding proteins (SSBPs) would most likely result in which of the following defects during DNA replication?

Accepted Answer

Destabilization of the unwound DNA, leading to premature re-annealing of the strands.

Question 11

Which of the following equations correctly represents the reaction catalyzed by DNA polymerase during chain elongation?

Accepted Answer

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

Question 12

During DNA replication, which enzyme is responsible for synthesizing the RNA primer required for DNA polymerase III to begin elongation?

Accepted Answer

Primase

Question 13

Which of the following is NOT a function of DNA polymerase III in E. coli?

Accepted Answer

Removal of RNA primers

Question 14

A patient is found to have a mutation that inactivates telomerase in their stem cells. Which of the following outcomes is most likely?

Accepted Answer

Progressive shortening of chromosome ends, leading to premature cellular aging.

Question 15

Which of the following best describes the role of the origin recognition complex (ORC) in eukaryotic DNA replication?

Accepted Answer

It tags the origin of replication as the site for initiation during the early G1 phase.

Question 16

Which of the following is a direct consequence if DNA ligase is nonfunctional during DNA replication?

Accepted Answer

Okazaki fragments on the lagging strand would remain unjoined.

Question 17

Which of the following statements about DNA synthesis is correct?

Accepted Answer

DNA synthesis occurs only in the 5' to 3' direction.

Question 18

Which of the following is a function of chromatin assembly factors (CAFs) during eukaryotic DNA replication?

Accepted Answer

They facilitate the re-association of histones with newly synthesized DNA.

Question 19

A researcher is studying a mutant E. coli strain that lacks 3' to 5' exonuclease activity in all DNA polymerases. What is the most likely consequence?

Accepted Answer

Increased mutation rate due to lack of proofreading during DNA replication.

DNA Replication and Recombination: Study Notes for Genetics Students

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