Question 1

Which experiment provided direct evidence that DNA, and not protein, is the genetic material in bacteriophages?

Accepted Answer

Hershey-Chase experiment

Question 2

According to Chargaff's rules, which of the following equations correctly represents the relationship between the bases in double-stranded DNA?

Accepted Answer

$A = T$ and $G = C$

Question 3

Which feature of DNA structure allows for the semiconservative replication observed in the Meselson-Stahl experiment?

Accepted Answer

Antiparallel double helix with complementary base pairing

Question 4

A mutation causes a defect in DNA ligase in a bacterial cell. Which process would be most directly affected?

Accepted Answer

Joining of Okazaki fragments during lagging strand synthesis

Question 5

Which enzyme is responsible for relieving the tension caused by supercoiling ahead of the replication fork?

Accepted Answer

Topoisomerase (Gyrase)

Question 6

During DNA replication in bacteria, which of the following is the correct sequence of events?

Accepted Answer

Primase synthesizes RNA primer, DNA polymerase III extends DNA, DNA ligase joins fragments

Question 7

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

Accepted Answer

They prevent re-annealing of separated DNA strands

Question 8

A scientist is using the Polymerase Chain Reaction (PCR) to amplify a segment of DNA. Which enzyme is essential for this process?

Accepted Answer

DNA polymerase (such as Taq polymerase)

Question 9

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

Accepted Answer

Shortening of telomeres after each cell division

Question 10

Which repair mechanism is most likely to fix a deaminated cytosine in DNA?

Accepted Answer

Base excision repair

Question 11

A patient is exposed to UV radiation, resulting in thymine dimers in their DNA. Which repair pathway is primarily responsible for removing these lesions?

Accepted Answer

Nucleotide excision repair

Question 12

Which of the following statements about bacterial plasmids is correct?

Accepted Answer

They are circular DNA molecules that can replicate independently of chromosomal DNA

Question 13

Which of the following is NOT a component of chromatin structure in eukaryotic cells?

Accepted Answer

Plasmids

Question 14

A cell is unable to progress from G2 to M phase. Which checkpoint is most likely malfunctioning?

Accepted Answer

G2/M checkpoint

Question 15

Which of the following mutagens is most likely to cause double-strand breaks in DNA?

Accepted Answer

Ionizing radiation

Question 16

Which DNA repair pathway is most error-prone and can lead to mutations at the site of repair?

Accepted Answer

Non-homologous end joining

Question 17

During DNA replication, which strand is synthesized discontinuously and why?

Accepted Answer

Lagging strand, because DNA polymerase can only synthesize DNA in the 5' to 3' direction

Question 18

Which of the following best explains the function of telomerase in eukaryotic cells?

Accepted Answer

It extends the 3' end of chromosomes to prevent loss of genetic material

Question 19

A researcher observes that a DNA sample denatures at a higher temperature than another sample. Which equation best explains this phenomenon?

Accepted Answer

Higher $G + C$ content increases melting temperature because $G \equiv C$ pairs have three hydrogen bonds

Question 20

Which process is most likely to use homologous recombination for DNA repair?

Accepted Answer

Repair of double-strand breaks using a sister chromatid as a template

DNA Structure, Chromosomes, and DNA Replication: Key Concepts and Mechanisms

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