Question 1

Which of the following best describes the structure of a DNA molecule as determined by Watson and Crick?

Accepted Answer

A double helix with anti-parallel strands and a sugar-phosphate backbone on the outside.

Question 2

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

Accepted Answer

$$20\%$$

Question 3

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

Accepted Answer

Topoisomerase

Question 4

What is the main function of telomerase in eukaryotic cells?

Accepted Answer

To add repetitive DNA sequences to the ends of chromosomes

Question 5

Which of the following statements about DNA replication is correct?

Accepted Answer

DNA polymerase III requires an RNA primer to begin synthesis.

Question 6

The Meselson-Stahl experiment provided evidence for which model of DNA replication?

Accepted Answer

Semiconservative

Question 7

Which of the following best explains why origins of replication are typically rich in AT base pairs?

Accepted Answer

AT pairs are easier to separate because they have only two hydrogen bonds.

Question 8

A mutation in the gene encoding DNA ligase would most likely result in which of the following problems during DNA replication?

Accepted Answer

Okazaki fragments not being joined together on the lagging strand

Question 9

Which of the following is a correct description of the directionality of DNA synthesis?

Accepted Answer

New nucleotides are added to the 3’ end of the growing strand.

Question 10

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

Accepted Answer

They stabilize unwound DNA strands to prevent re-annealing.

Question 11

If a cell lacked functional DNA polymerase I, what would be the most immediate consequence during DNA replication?

Accepted Answer

RNA primers would not be removed from the lagging strand.

Question 12

Which of the following is NOT a characteristic required of genetic material?

Accepted Answer

It must be able to catalyze metabolic reactions.

Question 13

Which of the following best explains why DNA is more stable than RNA?

Accepted Answer

DNA lacks a hydroxyl group at the 2’ carbon of the sugar.

Question 14

Which of the following statements about Okazaki fragments is correct?

Accepted Answer

They are short DNA fragments synthesized on the lagging strand.

Question 15

A scientist isolates a nucleic acid with the following composition: 20% adenine, 20% thymine, 30% guanine, and 30% cytosine. What can be concluded about this molecule?

Accepted Answer

It is likely double-stranded DNA.

Question 16

Which of the following best describes the energy source for the formation of phosphodiester bonds during DNA replication?

Accepted Answer

Cleavage of two phosphates from incoming deoxynucleoside triphosphates

Question 17

Which of the following is a direct result of the antiparallel arrangement of DNA strands?

Accepted Answer

One strand is synthesized continuously, and the other discontinuously.

Question 18

Which of the following experimental results from Meselson and Stahl ruled out the conservative model of DNA replication?

Accepted Answer

After one generation, all DNA was of intermediate density.

Question 19

Which enzyme is responsible for synthesizing short RNA primers during DNA replication?

Accepted Answer

Primase

Question 20

Why do stem cells and cancer cells have high telomerase activity?

Accepted Answer

To prevent chromosome shortening and allow unlimited cell divisions

The Molecular Basis of Inheritance: DNA Structure and Replication

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