DNA III: The Replication of DNA

A human body contains between 10 and 100 trillion cells. Each cell within a body contains the same DNA sequence (except on rare occasions). The reason each DNA sequence is identical is because

• a.the triphosphate nucleotides are the same in all cells.
• b.new DNA strands are made only by copying pre-existing DNA strands.
• c.there is only one pattern a DNA sequence can follow.
• d.there are only four nucleotides that make up a DNA sequence.

Which statement below BEST explains why biochemists often use in vitro reconstitution as a research method?

• a.It allows them to recreate a cellular event in isolation and manipulate it as necessary.
• b.It allows them to recreate and observe a cellular event in a natural environment.
• c.It allows them to recreate and observe a reproductive event within the human body.
• d.It allows them to recreate a biochemical event using only synthetic materials.

In the late 1970s, two research groups independently discovered what was responsible for separating the two strands of a DNA helix within a cell. The mechanism was identified as

• a.an enzyme called DNA ligase.
• b.an enzyme called DNA polymerase.
• c.an enzyme called DNA helicase.
• d.nucleotide triphosphates.

Select the comparison below that is accurate.

• a.DNA helicase is like a word processor.
• b.Nucleotide triphosphates are like wrecking balls.
• c.DNA polymerase is like a copy machine.
• d.Phosphate bonds are like building blocks.

Study the table shown below. Identify the sequence of discoveries that occurs in the correct order.

• a.A
• b.B
• c.C
• d.D

Which of the following could NOT have been discovered if the Kornberg team had not first identified the primer responsible for starting DNA synthesis?

• a.Nucleotides occur in complementary base-pairs.
• b.DNA synthesis is semi-conserative.
• c.Replication begins at specific origins.
• d.DNA synthesis is unidirectional.

Why are triphosphate nucleotides required for DNA synthesis?

• a.Each phosphate contributes energy and a total of three are needed for each step.
• b.The bridge between each nucleotide must be three phosphates long.
• c.The breaking of the high-energy bond between the 2^nd and 3^rd phosphates provides the energy for DNA synthesis.
• d.Only triphosphate nucleotides fit into both DNA helicase and Okazaki fragments.

Inside a cell, the primers that are necessary for DNA polymerase to start working are made of

• a.RNA.
• b.DNA primase.
• c.lagging strands.
• d.Okazaki fragments.