Question 1

Which experiment first demonstrated the phenomenon of transformation, where genetic material from one bacterial strain could change the phenotype of another?

Accepted Answer

Griffith's experiment with Streptococcus pneumoniae in mice

Question 2

In the Hershey-Chase experiment, which radioactive isotope was used to label DNA, and what was the key result?

Accepted Answer

$$^{32}P$$, and it was found inside the bacterial pellet

Question 3

Which of the following best describes the structure of DNA as determined by Watson and Crick?

Accepted Answer

A double helix with antiparallel sugar-phosphate backbones and complementary base pairing

Question 4

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

Accepted Answer

20%

Question 5

Which model of DNA replication was supported by the Meselson-Stahl experiment?

Accepted Answer

Semiconservative model

Question 6

During DNA replication, which enzyme is responsible for unwinding the double helix by breaking hydrogen bonds between bases?

Accepted Answer

Helicase

Question 7

What is the function of DNA ligase during DNA replication?

Accepted Answer

Joins Okazaki fragments on the lagging strand

Question 8

Why is DNA replication described as 'antiparallel'?

Accepted Answer

Because the two strands run in opposite 5' to 3' directions

Question 9

Which enzyme replaces RNA primers with DNA nucleotides during DNA replication?

Accepted Answer

DNA polymerase I

Question 10

What is the main reason eukaryotic chromosomes have multiple origins of replication?

Accepted Answer

To speed up the replication of large amounts of DNA

Question 11

Which of the following best explains why the lagging strand is synthesized in short fragments?

Accepted Answer

DNA polymerase can only add nucleotides to the 3' end, so synthesis must occur in segments as the fork opens

Question 12

What is the sequence of events for the enzymes involved in DNA replication on the lagging strand?

Accepted Answer

Helicase → Primase → DNA polymerase III → DNA polymerase I → Ligase

Question 13

Which of the following is a direct consequence of the inability to fully replicate the ends of linear DNA molecules in eukaryotes?

Accepted Answer

Shortening of telomeres with each cell division

Question 14

What is the function of telomerase in eukaryotic cells?

Accepted Answer

It extends the 3' ends of chromosomes to prevent loss of genetic material

Question 15

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

Accepted Answer

Hydrolysis of the two terminal phosphates from nucleoside triphosphates

Question 16

A mutation causes a cell to lack functional DNA ligase. Which of the following would most likely result?

Accepted Answer

Okazaki fragments on the lagging strand would not be joined

Question 17

Which of the following is NOT a function of DNA polymerase during replication?

Accepted Answer

Joining Okazaki fragments

Question 18

A scientist exposes cells to UV light, causing thymine dimers to form. Which enzyme is responsible for cutting out the damaged DNA segment?

Accepted Answer

Nuclease

Question 19

If a eukaryotic cell expressed telomerase in all of its somatic cells, what would be a likely consequence?

Accepted Answer

Increased risk of cancer due to unlimited cell division

Question 20

Which of the following best explains why DNA replication is highly accurate?

Accepted Answer

DNA polymerase proofreads and corrects mismatched bases

DNA Replication: History, Mechanism, and Enzymology

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