Question 1

Which experiment provided the first strong evidence that DNA, and not protein, is the genetic material in phages?

Accepted Answer

Hershey–Chase experiment

Question 2

According to Chargaff's rules, if a DNA sample contains 30% adenine, what percentage of guanine would you expect to find?

Accepted Answer

$$20\%$$

Question 3

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 new strand.

Question 4

What is the function of DNA ligase during DNA replication?

Accepted Answer

Joins Okazaki fragments on the lagging strand.

Question 5

A mutation occurs that disables the function of topoisomerase in a cell. What is the most likely consequence during DNA replication?

Accepted Answer

The DNA will become overwound ahead of the replication fork, stalling replication.

Question 6

Which of the following statements about the structure of DNA is correct?

Accepted Answer

The sugar-phosphate backbone runs antiparallel.

Question 7

During DNA replication in eukaryotes, why are multiple origins of replication necessary?

Accepted Answer

Eukaryotic chromosomes are much larger, so multiple origins speed up replication.

Question 8

Which enzyme is responsible for synthesizing the short RNA primer required for DNA polymerase to begin synthesis?

Accepted Answer

Primase

Question 9

A scientist exposes cells to X-rays, causing thymine dimers to form in the DNA. Which repair mechanism is most likely to fix this damage?

Accepted Answer

Nucleotide excision repair

Question 10

What is the main reason that linear eukaryotic chromosomes shorten with each round of DNA replication?

Accepted Answer

DNA polymerase cannot add nucleotides to the 5' end of a DNA strand.

Question 11

Which of the following best explains why telomerase is active in germ cells but not in most somatic cells?

Accepted Answer

Germ cells need to maintain chromosome length for future generations.

Question 12

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

Accepted Answer

One strand is synthesized continuously, the other discontinuously.

Question 13

A mutation in a gene encoding a histone protein would most likely affect which process?

Accepted Answer

Chromatin packing and gene expression

Question 14

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

Accepted Answer

They prevent the separated DNA strands from re-annealing.

Question 15

If a DNA molecule is 20% thymine, what is the percentage of cytosine?

Accepted Answer

$$30\%$$

Question 16

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

Accepted Answer

They can lead to genetic variation and evolution.

Question 17

In the Meselson-Stahl experiment, what result would you expect after two rounds of replication if DNA replication were dispersive?

Accepted Answer

A single band, but of lighter density than after the first round

Question 18

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

Accepted Answer

Its tight packing makes it inaccessible to transcription machinery.

Question 19

A patient has a genetic disorder caused by a defect in nucleotide excision repair. Which of the following symptoms would you most likely expect?

Accepted Answer

Increased susceptibility to UV-induced skin cancers

Question 20

Which of the following best describes the role of Okazaki fragments in DNA replication?

Accepted Answer

They are short DNA segments synthesized on the lagging strand.

The Molecular Basis of Inheritance: DNA Structure and Replication

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