Question 1

Which of the following best describes the semi-conservative model of DNA replication as supported by the Meselson-Stahl experiment?

Accepted Answer

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

Question 2

During which phase of the cell cycle does DNA replication occur in eukaryotic cells?

Accepted Answer

S phase

Question 3

What is the role of DNA polymerase during DNA replication?

Accepted Answer

It synthesizes new DNA by adding nucleotides to a growing strand.

Question 4

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

Accepted Answer

DNA ligase

Question 5

Why is the lagging strand synthesized discontinuously during DNA replication?

Accepted Answer

Because DNA polymerase can only synthesize DNA in the 5' to 3' direction and the replication fork opens in the opposite direction.

Question 6

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

Accepted Answer

Guanine–Cytosine

Question 7

What is the function of single-stranded binding (SSB) proteins during DNA replication?

Accepted Answer

They keep the DNA strands separated after helicase unwinds them.

Question 8

Which enzyme relieves the supercoiling tension generated ahead of the replication fork during DNA replication?

Accepted Answer

Topoisomerase

Question 9

What is the main reason eukaryotic chromosomes have telomeres?

Accepted Answer

To protect the ends of chromosomes from degradation and loss of important DNA during replication.

Question 10

Which enzyme extends the ends of linear chromosomes in eukaryotes by adding repetitive DNA sequences?

Accepted Answer

Telomerase

Question 11

If a DNA molecule has 30% adenine, what percentage of guanine would you expect according to Chargaff’s rules?

Accepted Answer

$$20\%$$

Question 12

Which of the following statements about DNA polymerase proofreading is correct?

Accepted Answer

DNA polymerase proofreads in the 3' to 5' direction using exonuclease activity.

Question 13

A mutation disables the primase enzyme in a cell. What is the most immediate effect on DNA replication?

Accepted Answer

No RNA primers are synthesized, so DNA polymerase cannot initiate DNA synthesis.

Question 14

Which of the following best explains why DNA replication is described as 'semi-discontinuous'?

Accepted Answer

One strand is synthesized continuously and the other discontinuously in fragments.

Question 15

In the Meselson-Stahl experiment, after two rounds of replication in $$^{14}N$$ medium, what proportion of DNA molecules are 'light' and what proportion are 'hybrid'?

Accepted Answer

75% are light, 25% are hybrid.

Question 16

Which of the following is NOT a required property of genetic material?

Accepted Answer

It must be composed of proteins.

Question 17

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

Accepted Answer

DNA is synthesized in the 5' to 3' direction.

Question 18

A diploid organism has two homologous chromosomes with alleles A and a for a gene. Which statement is correct?

Accepted Answer

The organism can have two different versions of the gene, one on each chromosome.

Question 19

Which of the following is a correct description of the chemical structure of DNA?

Accepted Answer

The sugar-phosphate backbone is on the outside, and bases are on the inside.

Question 20

Which of the following best explains the function of telomerase in eukaryotic cells?

Accepted Answer

It adds repetitive DNA sequences to the ends of chromosomes to prevent loss of genetic information.

DNA Replication: Mechanisms, Models, and Chromosome Structure

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