$$3'\text{-}TCGACGACT\text{-}5'$$

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 and radioactive labeling

Question 2

In the Hershey-Chase experiment, why was $$^{32}P$$ used to label DNA and $$^{35}S$$ used to label protein?

Accepted Answer

$$^{32}P is $$present in DNA but not in protein, and $$^{35}S is $$present in protein but not in DNA

Question 3

A mouse injected with heat-killed S strain and live R strain Streptococcus pneumoniae dies. What is the most likely explanation?

Accepted Answer

DNA from the heat-killed S cells was taken up by the live R cells, converting them to S cells

Question 4

Which feature of DNA structure allows for precise replication during cell division?

Accepted Answer

Complementary base pairing between antiparallel strands

Question 5

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

Accepted Answer

$$3'	ext{-}TCGACGACT	ext{-}5'$$

Question 6

Which model of DNA replication was supported by the Meselson-Stahl experiment?

Accepted Answer

Semiconservative replication

Question 7

During DNA replication, nucleotides are added to which end of the growing strand?

Accepted Answer

3' end

Question 8

What is the role of DNA ligase during DNA replication?

Accepted Answer

It catalyzes the final phosphodiester linkage between Okazaki fragments

Question 9

Why do eukaryotic chromosomes have multiple origins of replication?

Accepted Answer

To ensure rapid replication of large chromosomes

Question 10

What is the function of telomerase in stem cells?

Accepted Answer

It catalyzes the addition of lost telomeres to chromosome ends

Question 11

Which DNA repair mechanism is most likely to fix a mismatched base pair during replication?

Accepted Answer

Mismatch repair

Question 12

A patient with xeroderma pigmentosum (XP) is unable to repair DNA damage caused by UV light. Which repair system is defective?

Accepted Answer

Excision repair

Question 13

Cisplatin is effective in cancer therapy because it:

Accepted Answer

Cross-links DNA strands, preventing replication and causing cell death

Question 14

Which of the following best describes the antiparallel nature of DNA?

Accepted Answer

One strand runs $$5'\rightarrow 3'$$ and the other runs $$3'\rightarrow 5'$$

Question 15

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

Accepted Answer

DNA helicase

Question 16

What is the main reason Okazaki fragments are formed during DNA replication?

Accepted Answer

DNA polymerase can only add nucleotides to the 3' end, so the lagging strand is synthesized discontinuously

Question 17

Which of the following is a real-world consequence of telomere shortening in most somatic cells?

Accepted Answer

After many divisions, genes may be lost and the cell dies

Question 18

Which of the following statements about DNA polymerase is TRUE?

Accepted Answer

DNA polymerase is processive, catalyzing many linkages each time it binds to DNA

Question 19

A scientist is using PCR to amplify a DNA sequence. Which component is NOT required for the reaction?

Accepted Answer

DNA ligase

Question 20

Which of the following best explains why proteins were once thought to be the genetic material?

Accepted Answer

Proteins are more structurally diverse than DNA

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

Study Guide - Practice Questions