Question 1

Which experiment provided the first strong evidence that DNA, and not protein, is the genetic material responsible for heredity in bacteria?

Accepted Answer

Avery, McLeod, and McCarty's experiment using purified DNA from heat-killed bacteria

Question 2

In the Hershey-Chase experiment, why was radioactive phosphorus ($$^{32}P) $$used to label DNA, and not radioactive sulfur ($$^{35}S$$)?

Accepted Answer

Phosphorus is found in DNA but not in proteins, while sulfur is found in proteins but not in DNA

Question 3

Which of the following best describes the structure of DNA as determined by Watson and Crick?

Accepted Answer

A double helix with sugar-phosphate backbones on the outside and nitrogenous bases paired on the inside

Question 4

If a segment of DNA has the sequence 5'-AAGCTT-3', what is the complementary sequence on the other strand (written 5' to 3')?

Accepted Answer

5'-TTCGAA-3'

Question 5

During DNA replication, which enzyme is responsible for synthesizing short RNA primers needed to start the process?

Accepted Answer

Primase

Question 6

Meselson and Stahl's experiment with $$^{15}N$$ and $$^{14}N$$ isotopes demonstrated that DNA replication is:

Accepted Answer

Semiconservative

Question 7

Which of the following statements about Okazaki fragments is TRUE?

Accepted Answer

They are short DNA fragments synthesized on the lagging strand

Question 8

A mutation occurs that disables the proofreading function of DNA polymerase. What is the most likely consequence?

Accepted Answer

Increased frequency of mutations during DNA replication

Question 9

Which of the following best explains why telomeres are important for eukaryotic chromosomes?

Accepted Answer

They prevent the loss of important genetic information during DNA replication

Question 10

A scientist exposes bacterial cells to ultraviolet (UV) light, causing the formation of thymine dimers. Which DNA repair mechanism is most likely to fix this damage?

Accepted Answer

Nucleotide excision repair

Question 11

Which of the following is a direct result of the antiparallel structure of DNA?

Accepted Answer

DNA polymerase can only add nucleotides to the 3' end of a growing strand

Question 12

A patient is diagnosed with a genetic disorder caused by a defect in the enzyme that removes mismatched nucleotides after DNA replication. Which process is most likely impaired?

Accepted Answer

Mismatch repair

Question 13

Which of the following best describes the role of DNA ligase during DNA replication?

Accepted Answer

Joins Okazaki fragments together on the lagging strand

Question 14

In a DNA molecule, if 30% of the bases are adenine, what percentage of the bases are guanine?

Accepted Answer

20%

Question 15

Which of the following is a consequence of telomerase activity in cancer cells?

Accepted Answer

Unlimited cell division and potential for tumor growth

Question 16

A researcher is studying a bacteriophage that injects its genetic material into a bacterial cell. Which experiment would best determine whether the genetic material is DNA or protein?

Accepted Answer

Labeling the phage DNA with $$^{32}P$$ and the protein with $$^{35}S$$, then tracking which label enters the cell

Question 17

Which of the following statements about the leading and lagging strands during DNA replication is correct?

Accepted Answer

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

Question 18

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

Accepted Answer

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

Question 19

A cell is exposed to a chemical that causes frequent base-pair mismatches during DNA replication. Which repair mechanism is most likely to correct these errors immediately as they occur?

Accepted Answer

Proofreading by DNA polymerase

Question 20

Which of the following is a function of the enzyme helicase during DNA replication?

Accepted Answer

Unwinds the DNA double helix at the replication fork

DNA as the Genetic Material and Mechanisms of DNA Replication

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