Question 1

Which of the following correctly describes the difference between purines and pyrimidines in nucleic acids?

Accepted Answer

Purines have a double-ring structure, while pyrimidines have a single-ring structure.

Question 2

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

Accepted Answer

Helicase

Question 3

Which of the following base pairs is stabilized by three hydrogen bonds?

Accepted Answer

Guanine–Cytosine

Question 4

A scientist is analyzing a DNA fragment and finds that 30% of the bases are adenine. According to Chargaff's rules, what percentage of the bases should be guanine?

Accepted Answer

$$20\%$$

Question 5

Which of the following best explains why DNA synthesis is 'discontinuous' on the lagging strand?

Accepted Answer

DNA polymerase can only add nucleotides to the 3' end, so the lagging strand is synthesized in short fragments away from the replication fork.

Question 6

Which enzyme is responsible for joining Okazaki fragments during DNA replication?

Accepted Answer

Ligase

Question 7

In a DNA molecule, the 5' end of a strand is characterized by which of the following chemical groups?

Accepted Answer

A free phosphate group ($$-PO_4$^{3-})$$

Question 8

Which of the following statements about DNA replication in prokaryotes and eukaryotes is correct?

Accepted Answer

Eukaryotes have multiple origins of replication per chromosome, while prokaryotes typically have a single origin.

Question 9

A mutation in the gene encoding single-stranded binding proteins (SSBPs) would most likely result in which of the following problems during DNA replication?

Accepted Answer

The separated DNA strands would re-anneal prematurely, preventing replication.

Question 10

Which of the following best describes the function of DNA polymerase during replication?

Accepted Answer

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

Question 11

During DNA replication, which direction does DNA polymerase synthesize the new strand?

Accepted Answer

5' to 3'

Question 12

Which of the following is the correct sequence of events at a replication fork?

Accepted Answer

Helicase unwinds DNA, SSBPs stabilize single strands, primase synthesizes RNA primer, DNA polymerase extends DNA, ligase joins fragments.

Question 13

A patient is diagnosed with a genetic disorder that affects the function of topoisomerase. Which of the following problems would most likely occur during DNA replication?

Accepted Answer

Supercoiling ahead of the replication fork would inhibit DNA unwinding.

Question 14

Which of the following best describes the role of primase in DNA replication?

Accepted Answer

It synthesizes short RNA primers to provide a starting point for DNA polymerase.

Question 15

If a DNA molecule is 1000 base pairs long and contains 300 guanine bases, how many thymine bases does it contain?

Accepted Answer

$$200$$

Question 16

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

Accepted Answer

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

Question 17

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

Accepted Answer

Ribose sugar

Question 18

A researcher is studying DNA replication and wants to identify the leading and lagging strands at a replication fork. Which of the following statements 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 19

Which of the following best describes the energy source for DNA polymerization during replication?

Accepted Answer

Hydrolysis of the phosphate bonds in deoxynucleoside triphosphates ($$dNTPs)$$

Question 20

Which of the following is a correct complementary base pairing in DNA?

Accepted Answer

Adenine pairs with thymine

DNA Structure and Replication: Study Guide Notes

Guida di studio - Domande di pratica

Study guide - Flashcard