Question 1

Which experiment provided the first strong evidence that DNA, not protein, is the hereditary material in cells?

Accepted Answer

Hershey-Chase experiment using bacteriophages

Question 2

Which of the following best describes the chemical difference between DNA and RNA sugars?

Accepted Answer

DNA contains deoxyribose, which lacks an oxygen atom at the 2' carbon compared to ribose in RNA.

Question 3

According to Chargaff's rules, if a DNA sample contains 30% adenine, what percentage of guanine would you expect?

Accepted Answer

$$20\%$$

Question 4

Which feature of DNA structure allows it to be easily separated during replication and transcription?

Accepted Answer

Hydrogen bonds between base pairs are weak compared to covalent bonds.

Question 5

Which enzyme is responsible for relieving supercoiling ahead of the replication fork during DNA replication?

Accepted Answer

Topoisomerase

Question 6

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

Accepted Answer

The lagging strand, because DNA polymerase can only add nucleotides in the $$5' \rightarrow 3'$$ direction.

Question 7

Which of the following best explains why prokaryotic DNA replication is generally faster than eukaryotic DNA replication?

Accepted Answer

Prokaryotes have smaller genomes and less complex DNA packaging.

Question 8

A mutation disables the primase enzyme in a cell. Which immediate effect would you expect during DNA replication?

Accepted Answer

DNA polymerase cannot initiate synthesis because no RNA primers are available.

Question 9

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

Accepted Answer

DNA polymerase adds nucleotides only to the $$3'$$ end of a growing strand.

Question 10

Which of the following best describes the semi-conservative nature of DNA replication?

Accepted Answer

Each daughter DNA molecule contains one parental and one newly synthesized strand.

Question 11

Rosalind Franklin's X-ray crystallography data was crucial for which aspect of DNA discovery?

Accepted Answer

Revealing the helical structure and dimensions of DNA

Question 12

Which of the following is a purine base found in DNA?

Accepted Answer

Adenine

Question 13

In eukaryotic cells, why are there multiple origins of replication per chromosome?

Accepted Answer

To allow rapid and efficient replication of large, linear chromosomes.

Question 14

Which enzyme is responsible for joining Okazaki fragments on the lagging strand during DNA replication?

Accepted Answer

DNA ligase

Question 15

A scientist is comparing the base composition of two DNA samples. Sample 1 has 28% cytosine. According to Chargaff's rules, what percentage of thymine would you expect in Sample 1?

Accepted Answer

$$22\%$$

Question 16

Which of the following best explains why hydrogen bonds are important in the DNA double helix?

Accepted Answer

They are weak enough to allow strand separation but strong enough to stabilize base pairing.

Question 17

Which of the following is a key difference between prokaryotic and eukaryotic DNA replication?

Accepted Answer

Prokaryotes typically have one origin of replication per chromosome, while eukaryotes have multiple.

Question 18

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

Accepted Answer

They stabilize unwound DNA strands and prevent them from re-annealing.

Question 19

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

Accepted Answer

Joining of Okazaki fragments on the lagging strand

Question 20

Which of the following best explains why DNA replication is described as a 'zipper analogy'?

Accepted Answer

Helicase separates the two DNA strands like unzipping a jacket zipper.

DNA Structure & Replication: Essentials and Mechanisms

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