Question 1

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

Accepted Answer

Griffith's experiment with Streptococcus pneumoniae

Question 2

In the Hershey-Chase experiment, which radioactive label was found inside the bacterial cells, indicating the genetic material of the phage?

Accepted Answer

Radioactive phosphorus ($$^{32}P)$$

Question 3

Chargaff’s rules state that in any DNA molecule, the amount of adenine (A) is equal to the amount of thymine (T), and the amount of guanine (G) is equal to the amount of cytosine (C). If a DNA sample contains 30% adenine, what percentage of guanine does it contain?

Accepted Answer

$$20\%$$

Question 4

Which of the following best describes the semiconservative model of DNA replication?

Accepted Answer

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

Question 5

Which enzyme is responsible for relieving the strain caused by unwinding of the DNA double helix during replication?

Accepted Answer

Topoisomerase

Question 6

During DNA replication, why is an RNA primer necessary?

Accepted Answer

DNA polymerase can only add nucleotides to an existing 3' end.

Question 7

Which of the following statements about Okazaki fragments is correct?

Accepted Answer

They are joined together by DNA ligase on the lagging strand.

Question 8

A mutation occurs that disables the proofreading function of DNA polymerase. What is the most likely consequence?

Accepted Answer

The error rate during DNA replication will increase.

Question 9

Why do eukaryotic chromosomes have telomeres at their ends?

Accepted Answer

To postpone the erosion of genes near the ends of DNA molecules

Question 10

Which enzyme catalyzes the lengthening of telomeres in germ cells?

Accepted Answer

Telomerase

Question 11

A scientist isolates a DNA molecule and finds that it is circular, double-stranded, and associated with a small amount of protein. This DNA most likely comes from:

Accepted Answer

A bacterial cell

Question 12

Which of the following best explains why heterochromatin is generally transcriptionally inactive?

Accepted Answer

It is highly condensed, making DNA inaccessible to transcription machinery.

Question 13

Which chemical modification of histones is most likely to result in increased gene expression?

Accepted Answer

Acetylation of histone tails

Question 14

If a eukaryotic cell is exposed to a chemical that inhibits DNA ligase, which process will be most directly affected?

Accepted Answer

Joining of Okazaki fragments on the lagging strand

Question 15

Which of the following is a direct result of the antiparallel structure of DNA?

Accepted Answer

One strand is synthesized continuously, and the other discontinuously.

Question 16

A patient is exposed to high levels of X-rays, which cause DNA damage. Which DNA repair mechanism is most likely to remove and replace the damaged DNA?

Accepted Answer

Nucleotide excision repair

Question 17

Which of the following best describes the role of single-strand binding proteins during DNA replication?

Accepted Answer

They bind to and stabilize single-stranded DNA.

Question 18

Which of the following is a source of genetic variation that can be acted upon by natural selection?

Accepted Answer

Mutations that are not repaired and become permanent in the DNA sequence

Question 19

A DNA molecule is found to have 18% cytosine. According to Chargaff’s rules, what is the percentage of thymine in this DNA?

Accepted Answer

$$32\%$$

Question 20

Which of the following best explains why DNA polymerase cannot replicate the very ends of linear chromosomes?

Accepted Answer

There is no 3' end available for DNA polymerase to add nucleotides to after removal of the RNA primer.

The Molecular Basis of Inheritance: Structure, Replication, and Packaging of DNA

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