$$1 \times 10$$^{-10}$$ errors per nucleotide

Question 1

Which of the following features distinguishes DNA from RNA and contributes to DNA's greater stability in the cell?

Accepted Answer

DNA has a double-stranded structure and lacks a 2' hydroxyl group, reducing its reactivity.

Question 2

During agarose gel electrophoresis, which property of DNA fragments determines their migration speed through the gel?

Accepted Answer

The length of the DNA fragment, with shorter fragments migrating faster.

Question 3

In the Meselson-Stahl experiment, what evidence supported the semi-conservative model of DNA replication?

Accepted Answer

After one round of replication, DNA showed an intermediate density, and after two rounds, both intermediate and light DNA were present.

Question 4

Which enzyme is responsible for synthesizing the RNA primer required for DNA replication, and what is the main function of this primer?

Accepted Answer

Primase; it provides a free 3' hydroxyl group for DNA polymerase to begin synthesis.

Question 5

Which of the following best describes the role of single-stranded binding proteins (SSBs) during DNA replication?

Accepted Answer

They prevent the re-annealing of separated DNA strands, stabilizing the replication fork.

Question 6

A mutation in the gene encoding DNA ligase would most directly affect which step of DNA replication?

Accepted Answer

Joining of Okazaki fragments on the lagging strand.

Question 7

Which of the following statements about Okazaki fragments is correct?

Accepted Answer

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

Question 8

During nucleotide excision repair, which of the following steps occurs first?

Accepted Answer

A multi-enzyme complex recognizes and excises the damaged DNA segment.

Question 9

Which equation correctly represents the error rate of DNA polymerase with proofreading activity?

Accepted Answer

$$1 	imes 10$$^{-10}$$ errors per nucleotide

Question 10

Which of the following best explains why circular bacterial chromosomes can initiate multiple rounds of replication before cell division?

Accepted Answer

Replication can re-initiate at the origin before the previous round is complete, allowing overlapping cycles.

Question 11

Which of the following is NOT a direct function of the clamp loader complex during DNA replication?

Accepted Answer

Synthesizing new DNA strands by adding nucleotides.

Question 12

Which of the following statements about telomerase is TRUE?

Accepted Answer

Telomerase is a reverse transcriptase that extends telomeres using an RNA template.

Question 13

Which of the following best describes the role of DNA helicase during replication?

Accepted Answer

It unwinds the DNA double helix ahead of the replication fork.

Question 14

Which of the following is a consequence of a mutation that impairs the proofreading activity of DNA polymerase?

Accepted Answer

Higher frequency of base substitution mutations in the newly synthesized DNA.

Question 15

Which of the following best explains why DNA replication is considered 'asymmetrical' at the replication fork?

Accepted Answer

The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously.

Question 16

Which of the following is the correct order of events during base excision repair?

Accepted Answer

Glycosylase removes the damaged base, endonuclease cuts the DNA backbone, DNA polymerase fills the gap, DNA ligase seals the nick.

Question 17

Which of the following statements about the origin recognition complex (ORC) in eukaryotic cells is correct?

Accepted Answer

The ORC binds to the origin of replication and recruits other proteins to initiate DNA synthesis.

Question 18

Which of the following best describes the energy source for DNA polymerization?

Accepted Answer

Hydrolysis of the pyrophosphate released from dNTPs during nucleotide addition.

Question 19

Which of the following is a real-world consequence of errors in DNA replication that escape proofreading and repair?

Accepted Answer

Development of genetic mutations that can lead to cancer or inherited diseases.

Comprehensive Study Guide: DNA, RNA, Replication, Repair, Transcription, and Translation

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