Question 1

Which experiment provided the first strong evidence that DNA is the genetic material responsible for inheritance?

Accepted Answer

Griffith's transformation experiment with Streptococcus pneumoniae

Question 2

In Griffith's experiment, what was the result when heat-killed pathogenic S cells were mixed with living nonpathogenic R cells and injected into mice?

Accepted Answer

The mice died, and living S cells were recovered from them

Question 3

According to Chargaff's rules, which of the following is true for the base composition of DNA in any given species?

Accepted Answer

The amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine

Question 4

Which technique did Rosalind Franklin use to help reveal the double helical structure of DNA?

Accepted Answer

X-ray crystallography

Question 5

What is the significance of the antiparallel arrangement of the two DNA strands in the double helix?

Accepted Answer

It allows DNA polymerases to synthesize new strands only in the $$5' \rightarrow 3'$$ direction

Question 6

Which enzyme is responsible for unwinding the DNA double helix at the replication fork during DNA replication?

Accepted Answer

Helicase

Question 7

During DNA replication, why are Okazaki fragments formed on the lagging strand?

Accepted Answer

Because DNA polymerase can only synthesize DNA in the $$5' \rightarrow 3'$$ direction, requiring discontinuous synthesis away from the replication fork

Question 8

Which enzyme joins together Okazaki fragments during DNA replication?

Accepted Answer

DNA ligase

Question 9

What is the role of telomeres in eukaryotic chromosomes?

Accepted Answer

They postpone the erosion of genes near the ends of DNA molecules during replication

Question 10

A mutation occurs during DNA replication. Which repair mechanism is most likely to correct a mismatched base pair?

Accepted Answer

Mismatch repair

Question 11

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 12

Which protein relieves the strain caused by unwinding of the DNA double helix during replication?

Accepted Answer

Topoisomerase

Question 13

What is the function of histones in eukaryotic cells?

Accepted Answer

They help package DNA into nucleosomes, facilitating chromatin structure

Question 14

Which of the following statements about chromatin is correct?

Accepted Answer

Euchromatin is loosely packed and accessible for gene expression, while heterochromatin is tightly packed and less accessible

Question 15

Which of the following best explains why DNA polymerase requires a primer to begin synthesis?

Accepted Answer

DNA polymerase can only add nucleotides to an existing $$3'$$ hydroxyl group

Question 16

A scientist exposes cells to X-rays, causing damage to DNA. Which repair mechanism is most likely to remove and replace the damaged DNA segment?

Accepted Answer

Nucleotide excision repair

Question 17

Which of the following is a direct consequence of errors that escape DNA proofreading and repair mechanisms?

Accepted Answer

Mutations that contribute to genetic variation

Question 18

Which of the following equations correctly represents the relationship between the number of purines and pyrimidines in a double-stranded DNA molecule according to Chargaff's rules?

Accepted Answer

$$[A] + [G] = [T] + [C]$$

Question 19

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

Accepted Answer

They stabilize unwound DNA strands and prevent them from re-annealing

Question 20

A patient’s cells show abnormally short telomeres and premature aging. Which enzyme is most likely deficient in these cells?

Accepted Answer

Telomerase

Ch. 16 The Molecular Basis of Inheritance: DNA Structure, Replication, and Chromosome Organization

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