Question 1

Which experiment provided definitive evidence that DNA, and not protein, is the genetic material in phages infecting bacteria?

Accepted Answer

Alfred Hershey and Martha Chase's radioactive labeling experiment

Question 2

According to Chargaff’s rules, which equation correctly represents the relationship between base pairs in any species?

Accepted Answer

$$A = T$$ and $$G = C$$

Question 3

A scientist isolates DNA from a new species and finds that 30% of the bases are adenine. What percentage of the bases are cytosine?

Accepted Answer

20%

Question 4

Which structural feature of DNA ensures that the molecule has a uniform width, as revealed by X-ray crystallography?

Accepted Answer

Pairing of a purine with a pyrimidine

Question 5

What is the function of helicase during DNA replication?

Accepted Answer

Unwinds the parental double helix at replication forks

Question 6

During DNA replication, why is the lagging strand synthesized in fragments?

Accepted Answer

The lagging strand template runs in the 5' to 3' direction, requiring synthesis away from the replication fork

Question 7

Which enzyme is responsible for joining Okazaki fragments during DNA replication?

Accepted Answer

DNA ligase

Question 8

If a mutation occurs in the gene encoding DNA polymerase, which process would be most directly affected?

Accepted Answer

Proofreading and synthesis of new DNA strands

Question 9

Which equation best represents the directionality of DNA synthesis?

Accepted Answer

$$5' \rightarrow 3'$$

Question 10

A patient is exposed to X-rays, which cause DNA damage. Which repair mechanism is most likely to fix the resulting lesions?

Accepted Answer

Nucleotide excision repair

Question 11

Which protein relieves overwinding strain ahead of the replication fork during DNA replication?

Accepted Answer

Topoisomerase

Question 12

In the semiconservative model of DNA replication, what is the composition of each daughter DNA molecule after one round of replication?

Accepted Answer

Each contains one old strand and one new strand

Question 13

Which of the following best describes the role of histones in eukaryotic cells?

Accepted Answer

They are responsible for the main level of DNA packing in chromatin

Question 14

What is the effect of histone tail modifications on chromatin?

Accepted Answer

They result in changes in chromatin condensation and regulation of gene expression

Question 15

Which of the following is a real-world consequence of mutations that escape DNA repair mechanisms?

Accepted Answer

They are the source of genetic variation for natural selection

Question 16

Which of the following statements about nucleosomes is correct?

Accepted Answer

A nucleosome is composed of DNA wound twice around a core of eight histones

Question 17

Which enzyme initiates the synthesis of a new DNA strand by creating a short RNA primer?

Accepted Answer

Primase

Question 18

Why is dATP used as a building block in DNA synthesis instead of ATP?

Accepted Answer

dATP contains deoxyribose, which is required for DNA

Question 19

Which type of chromatin is highly condensed and difficult for the cell to express genetic information?

Accepted Answer

Heterochromatin

Question 20

A bacterial cell is exposed to a chemical that inhibits DNA ligase. What is the most likely outcome during DNA replication?

Accepted Answer

Okazaki fragments will not be joined, resulting in incomplete lagging strand synthesis

Chapter 16: The Molecular Basis of Inheritance – DNA Structure, Replication, and Chromosome Organization

Study Guide - Practice Questions