Question 1

According to Chargaff's rules, if a sample of DNA from an unknown organism contains 30% adenine, what percentage of guanine would you expect to find in the DNA?

Accepted Answer

20%

Question 2

Which of the following best describes the antiparallel orientation of DNA strands?

Accepted Answer

One strand runs 5’ to 3’, and the other runs 3’ to 5’.

Question 3

A scientist isolates a DNA molecule and finds that it contains 28% cytosine. According to Chargaff’s rules, what is the expected percentage of thymine in this DNA?

Accepted Answer

22%

Question 4

Which of the following statements about DNA polymerase is correct?

Accepted Answer

It adds nucleotides to the 3’ end of a growing DNA strand.

Question 5

During DNA replication, why is the lagging strand synthesized in short fragments?

Accepted Answer

Because DNA polymerase can only synthesize DNA in the 5’ to 3’ direction, and the lagging strand template is oriented 5’ to 3’ away from the replication fork.

Question 6

Which of the following best explains why DNA replication is considered semi-conservative?

Accepted Answer

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

Question 7

In eukaryotic cells, DNA replication begins at multiple origins of replication. What is the main advantage of this feature?

Accepted Answer

It allows the entire genome to be replicated more quickly.

Question 8

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

Accepted Answer

DNA ligase

Question 9

A mutation occurs during DNA replication, resulting in a mismatched base pair. If this mismatch is not repaired, what is the most likely outcome in the daughter cells?

Accepted Answer

One daughter cell will inherit the mutation, while the other will have the original sequence.

Question 10

Which of the following best describes the role of telomerase in eukaryotic cells?

Accepted Answer

It extends the ends of linear chromosomes to prevent loss of genetic material during replication.

Question 11

Which type of cell is most likely to have active telomerase?

Accepted Answer

Embryonic stem cells

Question 12

Which of the following DNA repair mechanisms is responsible for removing and replacing incorrectly paired nucleotides that escape proofreading during DNA replication?

Accepted Answer

Mismatch repair

Question 13

A patient is diagnosed with a genetic disorder caused by a defect in nucleotide excision repair. Which of the following symptoms is most likely to be observed?

Accepted Answer

Increased sensitivity to UV light and higher risk of skin cancer

Question 14

Which of the following statements about the energy source for DNA polymerization is correct?

Accepted Answer

The energy comes from the hydrolysis of the incoming deoxynucleoside triphosphate ($$dNTP) as it is $$added to the growing DNA strand.

Question 15

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 16

A researcher observes that after DNA replication, one daughter DNA molecule contains a mutation while the other does not. Which process most likely failed during replication?

Accepted Answer

Proofreading by DNA polymerase

Question 17

Which of the following is a direct consequence of the 5’ to 3’ directionality of DNA synthesis?

Accepted Answer

Okazaki fragments are formed on the lagging strand.

Question 18

Which of the following best describes the base pairing rules in DNA?

Accepted Answer

A pairs with T, and G pairs with C.

Question 19

A mutation in a bacterial cell prevents the formation of a single origin of replication. What is the most likely effect on DNA replication in this cell?

Accepted Answer

Replication will not initiate, and the cell will not divide.

Question 20

Which of the following steps is NOT part of the basic process of DNA repair?

Accepted Answer

Transcription of the damaged region

DNA Structure, Replication, and Repair: Study Notes

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