Question 1

Which experimental result from the Meselson-Stahl experiment provided the strongest evidence for the semiconservative model of DNA replication?

Accepted Answer

After one generation in 14N, DNA showed a single intermediate band between 15N and 14N.

Question 2

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 3

A mutation in which gene would most likely result in the inability to synthesize RNA primers during DNA replication in E. coli?

Accepted Answer

dnaG

Question 4

Which of the following best explains why the lagging strand is synthesized discontinuously?

Accepted Answer

DNA polymerase can only synthesize DNA in the 5' to 3' direction, but the lagging strand template is oriented 3' to 5'.

Question 5

Which property is unique to DNA polymerase I among the main E. coli DNA polymerases?

Accepted Answer

5' to 3' exonuclease activity

Question 6

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

Accepted Answer

They stabilize the unwound single-stranded DNA to prevent re-annealing.

Question 7

In eukaryotic cells, what is the main reason for having multiple origins of replication on each chromosome?

Accepted Answer

To ensure rapid and complete replication of large, linear chromosomes.

Question 8

Which enzyme is responsible for joining Okazaki fragments on the lagging strand during DNA replication?

Accepted Answer

DNA ligase

Question 9

A patient is diagnosed with Bloom syndrome, which is caused by a mutation in the gene encoding DNA helicase. Which of the following symptoms is most likely to be observed?

Accepted Answer

Proportional small size and increased cancer risk

Question 10

Which of the following best describes the role of telomerase in eukaryotic cells?

Accepted Answer

It extends the 3' end of the lagging strand template to prevent chromosome shortening.

Question 11

If a mutation eliminates the 3' to 5' exonuclease activity of DNA polymerase III, what is the most likely consequence?

Accepted Answer

The error rate during DNA replication would increase.

Question 12

Which of the following equations correctly represents the directionality of DNA synthesis?

Accepted Answer

$$5' \rightarrow 3'$$

Question 13

During DNA replication, which subunit of DNA polymerase III is responsible for 3' to 5' exonuclease activity?

Accepted Answer

The $$\varepsilon$$ subunit

Question 14

Which of the following is a direct consequence of the end-replication problem in eukaryotic cells?

Accepted Answer

Progressive shortening of chromosomes with each cell division

Question 15

Which of the following best explains why malignant cancer cells can divide indefinitely?

Accepted Answer

They maintain high telomerase activity, preventing telomere shortening.

Question 16

A researcher observes that a mutant E. coli strain cannot remove RNA primers from Okazaki fragments. Which enzyme is most likely defective in this strain?

Accepted Answer

DNA polymerase I

Question 17

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

Accepted Answer

Removal of RNA primers

Question 18

Which of the following best describes the process of chromatin remodeling during eukaryotic DNA replication?

Accepted Answer

Disassembly of nucleosomes ahead of the replication fork and reassembly onto daughter strands

Question 19

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.

DNA Replication: Mechanisms, Enzymes, and Regulation

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