Question 1

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

Accepted Answer

The Hershey-Chase experiment using bacteriophage T2 labeled with $$^{32}P$$ and $$^{35}S$$

Question 2

In the classic experiment by Avery, MacLeod, and McCarty, which treatment destroyed the transforming activity of the S strain extract?

Accepted Answer

Treatment with DNase

Question 3

Which of the following best describes the structure of DNA as revealed by X-ray diffraction and model building?

Accepted Answer

A right-handed double helix with antiparallel strands and complementary base pairing

Question 4

If a DNA strand has the sequence $$5'-AGCTGCTGA-3'$$, what is the sequence of the complementary strand?

Accepted Answer

$$3'-TCGACGACT-5'$$

Question 5

Which feature of DNA allows it to be precisely replicated during cell division?

Accepted Answer

Complementary base pairing between antiparallel strands

Question 6

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

Accepted Answer

DNA helicase

Question 7

What is the role of Okazaki fragments in DNA replication?

Accepted Answer

They are short DNA segments synthesized on the lagging strand

Question 8

Which enzyme catalyzes the final phosphodiester bond between Okazaki fragments?

Accepted Answer

DNA ligase

Question 9

Why do eukaryotic chromosomes have multiple origins of replication?

Accepted Answer

To ensure the entire chromosome is replicated quickly despite its large size

Question 10

What is the function of telomerase in stem cells?

Accepted Answer

It extends telomeres by adding repetitive DNA sequences to the ends of chromosomes

Question 11

Which DNA repair mechanism is most likely to fix a mismatched base pair immediately after DNA synthesis?

Accepted Answer

Proofreading by DNA polymerase

Question 12

A patient with xeroderma pigmentosum is highly sensitive to UV light because of a defect in which DNA repair system?

Accepted Answer

Excision repair

Question 13

Cisplatin is an effective anti-cancer drug because it:

Accepted Answer

Forms cross-links between DNA strands, blocking replication and leading to cell death

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

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

Accepted Answer

New nucleotides are always added to the 3' end of the growing DNA strand

Question 16

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

Accepted Answer

One strand is synthesized continuously and the other discontinuously during replication

Question 17

Which of the following best describes the role of the sliding DNA clamp in replication?

Accepted Answer

It keeps DNA polymerase attached to the DNA, increasing processivity

Question 18

A scientist is studying a cell line that lacks functional DNA ligase. Which process would be most directly affected?

Accepted Answer

Joining of Okazaki fragments on the lagging strand

Question 19

Which of the following is a consequence of the loss of telomeres during repeated cell divisions in most somatic cells?

Accepted Answer

Progressive shortening of chromosomes, eventually leading to cell death

Question 20

Which of the following best explains why the Meselson-Stahl experiment supported the semiconservative model of DNA replication?

Accepted Answer

After one generation, all DNA molecules had intermediate density, and after two generations, both light and intermediate DNA were present

DNA and Its Role in Heredity: Structure, Replication, and Repair

Study Guide - Practice Questions