Question 1

Which experiment provided the first direct evidence that DNA is the hereditary material responsible for transformation in bacteria?

Accepted Answer

Avery, MacLeod, and McCarty's experiment using enzymatic destruction of macromolecules

Question 2

In the Hershey-Chase experiment, why was $$^{32}P$$ used to label DNA and $$^{35}S$$ used to label protein?

Accepted Answer

DNA contains phosphorus but not sulfur, while proteins contain sulfur but not phosphorus

Question 3

Which of the following is NOT a property required of a hereditary molecule?

Accepted Answer

Ability to catalyze metabolic reactions

Question 4

According to Chargaff’s rules, which of the following equations is always true for double-stranded DNA?

Accepted Answer

$$A + G = T + C$$

Question 5

Which feature of the DNA double helix is critical for the accurate replication of genetic information?

Accepted Answer

Complementary base pairing between purines and pyrimidines

Question 6

What is the main function of DNA ligase during DNA replication?

Accepted Answer

Joining Okazaki fragments by forming phosphodiester bonds

Question 7

Which enzyme is responsible for relieving supercoiled tension ahead of the replication fork during DNA replication?

Accepted Answer

Topoisomerase

Question 8

Why is an RNA primer required for DNA replication?

Accepted Answer

DNA polymerase can only add nucleotides to an existing 3’ OH group

Question 9

Which of the following best describes the outcome of the Meselson-Stahl experiment?

Accepted Answer

DNA replication is semiconservative

Question 10

What is the role of telomerase in eukaryotic cells?

Accepted Answer

It adds repetitive DNA sequences to the ends of chromosomes to prevent shortening

Question 11

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

Accepted Answer

Proofreading is performed by the 3’ to 5’ exonuclease activity

Question 12

A mutation in the gene encoding DNA ligase would most likely result in which of the following?

Accepted Answer

Accumulation of nicks in the lagging strand

Question 13

Which of the following is a direct application of the Polymerase Chain Reaction (PCR) technique?

Accepted Answer

Amplifying specific DNA segments for forensic analysis

Question 14

In Sanger (dideoxy) sequencing, what is the effect of incorporating a dideoxynucleotide (ddNTP) into a growing DNA strand?

Accepted Answer

It terminates DNA strand elongation due to the absence of a 3’ OH group

Question 15

Which of the following best explains why most somatic cells lack telomerase activity?

Accepted Answer

To prevent uncontrolled cell division and tumor formation

Question 16

A scientist is analyzing a DNA sample and finds that it contains 30% adenine. According to Chargaff’s rules, what percentage of thymine should be present?

Accepted Answer

30%

Question 17

Which of the following is a consequence of the inability of DNA polymerase I to replace the last RNA primer at the end of a linear chromosome?

Accepted Answer

Chromosome shortening with each cell division

Question 18

Which property of the DNA double helix allows proteins to recognize specific sequences for binding?

Accepted Answer

The major and minor grooves

Question 19

Which enzyme is responsible for synthesizing the majority of new DNA during bacterial DNA replication?

Accepted Answer

DNA polymerase III

Question 20

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

Accepted Answer

It allows for faster and more efficient replication of large genomes

DNA Structure and Replication: Foundations of Molecular Genetics

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