Question 1

Which experiment provided the first direct evidence that DNA, and not protein, is the genetic material responsible for heredity in viruses?

Accepted Answer

Hershey and Chase's experiment using radioactive isotopes to label phage DNA and protein

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 structure of a DNA double helix?

Accepted Answer

Two antiparallel strands held together by hydrogen bonds between complementary bases

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 enzyme topoisomerase in a cell. What is the most likely consequence during DNA replication?

Accepted Answer

The DNA will become overwound and break due to increased tension ahead of the replication fork

Question 6

Which of the following statements about the leading and lagging strands during DNA replication is correct?

Accepted Answer

The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments

Question 7

Which enzyme is responsible for removing RNA primers and replacing them with DNA nucleotides during DNA replication in bacteria?

Accepted Answer

DNA polymerase I

Question 8

In the Meselson-Stahl experiment, what result would you expect after two rounds of DNA replication in a medium containing only $$^{14}N if $$DNA replication is semiconservative?

Accepted Answer

Half the DNA would be light and half would be intermediate density

Question 9

Which of the following best explains why mutations are important in evolution?

Accepted Answer

They are the source of genetic variation upon which natural selection acts

Question 10

A scientist is studying a eukaryotic chromosome. Which of the following structures would she expect to find as the first level of DNA packing?

Accepted Answer

Nucleosomes formed by DNA wrapped around histones

Question 11

During DNA replication, which direction does DNA polymerase add new nucleotides to the growing DNA strand?

Accepted Answer

5' to 3' direction

Question 12

Which of the following is a correct pairing of nitrogenous bases in DNA?

Accepted Answer

Adenine with thymine

Question 13

What is the role of single-strand binding proteins during DNA replication?

Accepted Answer

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

Question 14

Which of the following best describes the process of nucleotide excision repair?

Accepted Answer

A nuclease removes a damaged DNA segment, and the gap is filled by DNA polymerase and sealed by DNA ligase

Question 15

A patient is found to have a genetic disorder caused by a single base substitution in a gene. Which process most likely failed to correct this error during DNA replication?

Accepted Answer

Mismatch repair

Question 16

Which of the following statements about bacterial and eukaryotic chromosomes is correct?

Accepted Answer

Bacterial chromosomes are circular and supercoiled, while eukaryotic chromosomes are linear and packed with histones

Question 17

If a DNA molecule is composed of 18% cytosine, what is the percentage of thymine in the molecule?

Accepted Answer

$$32\%$$

Question 18

Which enzyme is responsible for synthesizing short RNA primers needed to start DNA synthesis?

Accepted Answer

Primase

Question 19

A mutation in the gene encoding DNA polymerase III would most directly affect which process?

Accepted Answer

Synthesis of new DNA strands by adding nucleotides to the 3' end

Question 20

Which of the following best explains why DNA replication is described as 'semiconservative'?

Accepted Answer

Each new DNA molecule consists of one parental strand and one newly synthesized strand

Chapter 16 Biology

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