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

In the Meselson-Stahl experiment, which isotope of nitrogen was used to distinguish between parental and daughter DNA strands?

Accepted Answer

$$^{15}N ($$heavy nitrogen)

Question 3

Which enzyme is responsible for unwinding the DNA double helix at the replication fork?

Accepted Answer

Helicase

Question 4

What is the primary function of DNA polymerase III in prokaryotic DNA replication?

Accepted Answer

Synthesizing new DNA strands by adding nucleotides to the 3' end of a primer

Question 5

Why is DNA replication considered to be bidirectional in bacteria?

Accepted Answer

Replication proceeds in both directions from the origin, forming two replication forks.

Question 6

Which of the following best explains the need for multiple origins of replication in eukaryotic chromosomes?

Accepted Answer

Eukaryotic chromosomes are large and linear, requiring multiple origins to ensure timely replication.

Question 7

What is the main role of the enzyme telomerase in eukaryotic cells?

Accepted Answer

It extends the 3' ends of linear chromosomes to prevent shortening during replication.

Question 8

During DNA replication, which strand is synthesized continuously and in the same direction as the replication fork movement?

Accepted Answer

Leading strand

Question 9

Which of the following statements about Okazaki fragments is correct?

Accepted Answer

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

Question 10

A mutation in the gene encoding DNA ligase would most likely result in which of the following defects during DNA replication?

Accepted Answer

Failure to join Okazaki fragments on the lagging strand

Question 11

Which of the following equations correctly represents the chemical reaction catalyzed by DNA polymerase during DNA synthesis?

Accepted Answer

$$(dNMP)_{(n)} + dNTP \rightarrow (dNMP)_{(n+1)} + PP_i$$

Question 12

In E. coli, which protein binds to the ter sequences to terminate DNA replication?

Accepted Answer

Tus protein

Question 13

Which of the following is a direct consequence if telomerase activity is lost in a human somatic cell?

Accepted Answer

The cell's chromosomes will become progressively shorter with each division.

Question 14

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

Accepted Answer

DNA polymerase can only add nucleotides to an existing 3' hydroxyl group.

Question 15

A patient is found to have a mutation that increases telomerase activity in their somatic cells. Which of the following is a likely consequence?

Accepted Answer

Increased risk of cancer due to unlimited cell division

Question 16

Which of the following is NOT a function of the DnaA protein in E. coli DNA replication?

Accepted Answer

Synthesizing new DNA strands

Question 17

Which of the following best describes the role of topoisomerase (DNA gyrase) during DNA replication?

Accepted Answer

It relieves supercoiling ahead of the replication fork.

Question 18

A researcher is studying a eukaryotic cell line with a mutation that prevents the removal of RNA primers. Which enzyme is most likely defective?

Accepted Answer

DNA polymerase I

Question 19

Which of the following statements about the directionality of DNA synthesis is correct?

Accepted Answer

DNA synthesis always proceeds in the 5' to 3' direction.

Question 20

A new drug inhibits the activity of single-stranded binding proteins (SSBs) during DNA replication. What is the most likely effect of this drug on DNA replication?

Accepted Answer

The separated DNA strands would re-anneal, preventing replication.

DNA Replication: Mechanisms and Models (Genetics Study Notes)

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