Question 1

Which of the following best describes the chemical structure of a DNA nucleotide?

Accepted Answer

A phosphate group, a deoxyribose sugar, and a nitrogenous base

Question 2

Which of the following statements about the Meselson-Stahl experiment is correct?

Accepted Answer

It demonstrated that DNA replication is semiconservative by showing that, after one round of replication in $$^{14}N$$ medium, DNA molecules had intermediate density.

Question 3

DNA polymerase requires several factors to synthesize new DNA. Which of the following is NOT required for DNA polymerase activity?

Accepted Answer

A free 5' phosphate group

Question 4

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

Accepted Answer

Helicase

Question 5

A patient has a mutation that prevents the formation of Okazaki fragments. Which process is most directly affected?

Accepted Answer

Synthesis of the lagging strand during DNA replication

Question 6

Which of the following equations correctly represents the base pairing in DNA?

Accepted Answer

$$A = T$$ and $$G = C$$

Question 7

Which feature distinguishes eukaryotic DNA replication from prokaryotic DNA replication?

Accepted Answer

Eukaryotic chromosomes have multiple origins of replication, while prokaryotic chromosomes typically have a single origin.

Question 8

Telomerase is essential for the replication of chromosome ends in eukaryotes. What is the primary function of telomerase?

Accepted Answer

It extends the 3' end of the template strand using an RNA template.

Question 9

A researcher adds DNA polymerase, dNTPs, and a DNA template to a reaction tube but observes no DNA synthesis. Which critical component is most likely missing?

Accepted Answer

A primer with a free 3' hydroxyl group

Question 10

Which of the following best explains why DNA replication is described as 'semiconservative'?

Accepted Answer

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

Question 11

During DNA replication, which enzyme is responsible for joining Okazaki fragments on the lagging strand?

Accepted Answer

DNA ligase

Question 12

A mutation in the gene encoding DNA polymerase I in E. coli would most likely result in which of the following defects?

Accepted Answer

Inability to remove RNA primers from Okazaki fragments

Question 13

If a DNA molecule has 30% adenine, what percentage of guanine would you expect to find?

Accepted Answer

$$20\%$$

Question 14

Which of the following is a key difference between the synthesis of the leading and lagging strands during DNA replication?

Accepted Answer

The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments.

Question 15

A scientist is studying a eukaryotic cell line with abnormally short telomeres. Which of the following is the most likely explanation?

Accepted Answer

Reduced activity of telomerase

Question 16

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

Accepted Answer

DNA is synthesized in the 5' to 3' direction.

Question 17

A patient is diagnosed with a rare genetic disorder in which their cells accumulate supercoiled DNA during replication. Which enzyme is most likely defective?

Accepted Answer

Topoisomerase

Question 18

In a DNA replication experiment, a scientist observes that DNA synthesis stalls soon after initiation. Which of the following is the most likely cause?

Accepted Answer

Primase is not synthesizing RNA primers.

Question 19

Which of the following statements about DNA polymerase is correct?

Accepted Answer

It adds nucleotides to the 3' end of a growing DNA strand.

Question 20

A forensic scientist is analyzing a DNA sample and finds that the ratio of purines to pyrimidines is not 1:1. What is the most likely explanation?

Accepted Answer

The sample is contaminated or degraded, as in normal double-stranded DNA $$A + G = T + C.$$

DNA Structure and Replication: Study Guide

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