Question 1

Which experiment provided definitive evidence that genes are composed of DNA rather than protein?

Accepted Answer

Hershey and Chase experiment

Question 2

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

Accepted Answer

$$^{35}P$$

Question 3

What is the correct description of the structure of a deoxyribonucleotide?

Accepted Answer

A phosphate group attached to the 5' carbon, a deoxyribose sugar, and a nitrogenous base

Question 4

Which of the following best explains why DNA strands are described as antiparallel?

Accepted Answer

One strand runs 5' to 3', while the other runs 3' to 5'

Question 5

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

Accepted Answer

Semiconservative replication

Question 6

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

Accepted Answer

5' to 3'

Question 7

What is the function of DNA helicase during DNA replication?

Accepted Answer

Catalyzes the separation of DNA strands to open the double helix

Question 8

Why is primase necessary for DNA replication?

Accepted Answer

It provides a starting point for DNA polymerase by synthesizing an RNA primer

Question 9

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

Accepted Answer

DNA ligase

Question 10

What is the primary function of single-strand DNA-binding proteins (SSBPs) during DNA replication?

Accepted Answer

They stabilize single-stranded DNA to prevent reformation of the double helix

Question 11

Which enzyme relieves the tension ahead of the replication fork caused by the unwinding of DNA?

Accepted Answer

Topoisomerase

Question 12

Why does the lagging strand become shorter after each round of DNA replication in linear chromosomes?

Accepted Answer

The final RNA primer is removed and cannot be replaced with DNA, leaving a gap

Question 13

Which cell types have fully active telomerase, allowing for complete replication of chromosome ends?

Accepted Answer

Germ cells and stem cells

Question 14

What is the role of DNA polymerase's exonuclease activity?

Accepted Answer

It removes mismatched bases during proofreading

Question 15

Which DNA repair mechanism is defective in individuals with Xeroderma pigmentosum (XP)?

Accepted Answer

Nucleotide excision repair

Question 16

A patient is exposed to excessive UV light and develops skin lesions. Which DNA damage is most likely responsible?

Accepted Answer

Formation of thymine dimers

Question 17

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

Accepted Answer

Cleavage of pyrophosphate from incoming dNTPs

Question 18

In eukaryotic cells, what is the significance of having multiple origins of replication?

Accepted Answer

It allows for faster and more efficient replication of large linear chromosomes

Question 19

Which protein complex contains all the enzymes responsible for DNA synthesis around the replication fork?

Accepted Answer

Replisome

Question 20

A scientist observes that after DNA replication, the daughter DNA contains alternating segments of parental and newly synthesized DNA. Which model does this observation support?

Accepted Answer

Dispersive model

DNA and the Gene: Synthesis and Repair – Study Notes

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