Chapter Test: DNA

Frederic Griffith used the word transformation to describe the changes in bacteria that he observed. Which is the most useful definition of transformation?

• a. a permanent change in gene expression

• b. a permanent change in the function or activity of a cell

• c. a temporary change in the genetic composition of an organism

• d. a permanent change in the genetic composition of an organism

In the Hershey-Chase experiment, the components of bacteriophages were labeled with radioactive isotopes of sulfur and phosphorus. What was the Hershey-Chase experiment designed to determine?

• whether or not bacteriophages can infect bacteria

• whether DNA or RNA is the genetic material of the virus

• whether cells use DNA or proteins to store genetic information

• whether or not viruses satisfy the criteria for life

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The result of the Hershey-Chase experiment was that radioactivity could be detected inside the bacterial cells when they were infected by bacteriophages marked with phosphorus-32. What did the investigators conclude from this result?

• Bacteriophages inject their DNA into the bacterial cells.

• Bacteriophages inject their protein into the bacterial cells.

• Bacteriophages inject carbohydrates into the bacterial cells.

• Bacteriophages absorb DNA from bacterial cells.

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If 35% of an organism’s DNA is thymine, what is the percentage of guanine?

• 15%

• 35%

• 70%

• 50%

Chargaff's rules of base pairing are explained by which structural feature of DNA?

• Each strand of DNA contains a phosphate and sugar backbone.

• The nucleotides of DNA may be arranged in a wide variety of sequences.

• DNA is double stranded, and covalent bonds between identical nucleotides hold the two strands together.

• DNA is double stranded, and hydrogen bonds between base pairs hold the two strands together.

The model of the double-helix model of the DNA molecule resembles a twisted ladder. What makes up the rungs of the twisted ladder?

• paired phosphate groups

• paired nitrogenous bases

• paired sugars

• hydrogen and oxygen atoms

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This figure shows a section of a double-stranded DNA molecule. What aspects of the structure of DNA are explained by this model? Select three answer choices.

• Paired nucleotides are held together by covalent bonds.

• Adenine is paired with thymine and guanine is paired with cytosine.

• Paired nucleotides are held together by hydrogen bonds.

• The two strands of DNA each have phosphate-sugar backbones.

• The numbers of each nucleotide determine genetic information.

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How does the double-helical structure of DNA explain how the molecules can be copied or replicated?

• Because of base pairing, each strand has all the information to serve as a template for the synthesis of the other strand.

• Each strand receives the information from the DNA polymerase attached to the replication fork.

• The nitrogenous bases on one strand are copied to the other strand.

• The nitrogenous bases line up on each strand and are attached to each other.

As cells pass through the cell cycle, their volume of DNA alternately halves and doubles. Which statement about DNA correctly explains this pattern?

• DNA replication occurs during all phases of the cell cycle.

• DNA replication occurs only during the G1 phase of the cell cycle.

• DNA replication occurs only during the S phase of the cell cycle.

• DNA replication occurs randomly, and is unrelated to the cell cycle.

A scientist uses radioactive isotopes to label a double-stranded molecule of DNA. Then the DNA undergoes replication in a non-radioactive medium. Where are the two original radioactive strands of DNA?

• Both strands are broken apart.

• Both strands are intact, and both are part of the same molecule of DNA.

• One strand is intact, and the other strand is broken apart and distributed among the new DNA molecules.

• Both strands are broken apart, and their pieces are distributed among the new DNA molecules.