Question 1

Which model of DNA replication is supported by the Meselson-Stahl experiment, and what is the key feature of this model?

Accepted Answer

Semiconservative replication; each daughter DNA molecule contains one parental and one new strand

Question 2

During bacterial DNA replication, which protein is responsible for unwinding the DNA double helix at the replication fork?

Accepted Answer

DNA helicase (DnaB)

Question 3

What is the primary function of DNA topoisomerase during DNA replication?

Accepted Answer

Relaxing supercoiling ahead of the replication fork

Question 4

Why are the sequence motifs at the origin of replication in E. coli often AT-rich?

Accepted Answer

AT pairs are easier to separate due to having only two hydrogen bonds

Question 5

Which enzyme is responsible for removing RNA primers and replacing them with DNA nucleotides in prokaryotic DNA replication?

Accepted Answer

DNA polymerase I

Question 6

In eukaryotic DNA replication, what is the main enzyme responsible for synthesizing the leading strand?

Accepted Answer

DNA polymerase epsilon (Pol ε)

Question 7

What is the 'end-replication problem' in eukaryotes, and how is it solved?

Accepted Answer

Lagging strand cannot be fully replicated at chromosome ends; solved by telomerase adding telomere repeats

Question 8

Which of the following best describes the directionality of DNA synthesis by DNA polymerases?

Accepted Answer

5' to 3' direction only

Question 9

A mutation in the gene encoding the beta subunit of DNA polymerase III in E. coli would most likely result in which of the following?

Accepted Answer

Reduced processivity and slower DNA synthesis

Question 10

Which of the following equations correctly represents the exponential amplification of DNA during PCR, where $$n is $$the number of cycles?

Accepted Answer

$$2^n$$

Question 11

During Sanger sequencing, what is the role of dideoxynucleotides (ddNTPs)?

Accepted Answer

They terminate DNA strand elongation by lacking a 3'-OH group

Question 12

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

Accepted Answer

DNA ligase

Question 13

A patient’s cells show rapid telomere shortening and early cell senescence. Which enzyme is most likely deficient or inactive in these cells?

Accepted Answer

Telomerase

Question 14

Which of the following statements about Okazaki fragments is correct?

Accepted Answer

They are short DNA fragments synthesized on the lagging strand

Question 15

In a PCR reaction, which component is responsible for withstanding the high temperatures used during the denaturation step?

Accepted Answer

Taq DNA polymerase

Question 16

Which of the following best explains why DNA polymerase requires an RNA primer to begin synthesis?

Accepted Answer

DNA polymerase can only add nucleotides to an existing 3'-OH group

Question 17

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

Accepted Answer

Prokaryotes have a single origin of replication, eukaryotes have multiple origins

Question 18

A researcher is analyzing a gel after PCR amplification of a VNTR locus. What does the presence of multiple bands in a single individual’s lane most likely indicate?

Accepted Answer

The individual is heterozygous at the VNTR locus

Question 19

Which of the following best describes the proofreading activity of DNA polymerases?

Accepted Answer

3' to 5' exonuclease activity

Question 20

If a mutation prevents the function of the Tus protein in E. coli, what is the most likely consequence?

Accepted Answer

Replication forks will not terminate properly at the ter sites

DNA Replication: Mechanisms, Enzymes, and Applications

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