Q: Which of the following equations correctly represents the base pairing in double-stranded DNA according to Chargaff's rules?

$\text{[A]} = \text{[T]}$ and $\text{[G]} = \text{[C]}$

Question 1

Which experiment provided the most direct evidence that DNA is the genetic material in cells?

Accepted Answer

Hershey and Chase's experiment using bacteriophages and radioactive labeling

Question 2

According to Chargaff's rules, if a DNA molecule contains 30% adenine, what percentage of cytosine does it contain?

Accepted Answer

20%

Question 3

Which of the following best describes the semiconservative model of DNA replication?

Accepted Answer

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

Question 4

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

Accepted Answer

Helicase

Question 5

During DNA replication, which enzyme synthesizes short RNA primers to initiate synthesis?

Accepted Answer

Primase

Question 6

What is the function of single-strand binding proteins (SSBs) during DNA replication?

Accepted Answer

They prevent the separated DNA strands from reannealing.

Question 7

Which enzyme joins Okazaki fragments on the lagging strand during DNA replication?

Accepted Answer

Ligase

Question 8

A mutation in the gene encoding DNA polymerase I would most directly affect which process during DNA replication?

Accepted Answer

Removal of RNA primers and replacement with DNA nucleotides

Question 9

Which of the following best explains why the lagging strand is synthesized discontinuously?

Accepted Answer

DNA polymerase can only add nucleotides in the 5' to 3' direction, requiring synthesis away from the replication fork.

Question 10

Which structure is responsible for relieving the tension caused by unwinding of the DNA helix?

Accepted Answer

Topoisomerase

Question 11

If a cell is unable to produce telomerase, what is the most likely consequence?

Accepted Answer

Progressive shortening of chromosome ends with each cell division

Question 12

Which of the following is NOT a component of a DNA nucleotide?

Accepted Answer

Ribose sugar

Question 13

Which process describes the uptake of foreign DNA by a bacterial cell?

Accepted Answer

Transformation

Question 14

Which of the following equations correctly represents the base pairing in double-stranded DNA according to Chargaff's rules?

Accepted Answer

$	ext{[A]} = 	ext{[T]}$ and $	ext{[G]} = 	ext{[C]}$

Question 15

A scientist isolates a DNA molecule and finds that it contains 18% guanine. What percentage of thymine does it contain?

Accepted Answer

32%

Question 16

Which of the following best describes the role of histones in eukaryotic chromosomal compaction?

Accepted Answer

Histones package DNA into nucleosomes, facilitating chromatin structure and compaction.

Question 17

Which enzyme is primarily responsible for synthesizing the new DNA strand during replication in prokaryotes?

Accepted Answer

DNA polymerase III

Question 18

A patient is diagnosed with a genetic disorder that impairs nucleotide excision repair. Which cellular process is most likely affected?

Accepted Answer

Repair of DNA damage caused by UV light

Question 19

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

Accepted Answer

The leading strand is synthesized continuously toward the replication fork, while the lagging strand is synthesized discontinuously away from the fork.

Question 20

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.

L16: Nucleic Acid Structure and DNA Replication

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