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DNA Replication

Why is a pre-existing DNA strand necessary for the action of DNA polymerase? DNA polymerase uses the complementary nature of DNA strands to replicate DNA. The polymerase enzyme does not contain any information about the order of base sequences. Without a template strand of DNA the enzyme is incapable of selecting which base to add to the sequence next. DNA polymerase binds to a DNA strands and adds new material to it in order to build a complementary strand. The complementary nature of the four bases provides the information to build the correct sequence guanines, cytosines, adenines, and thymines.

View the animation below, then complete the quiz to test your knowledge of the concept.

1Which of the following are limitations of DNA polymerase?
A)it can only add bases to the exposed 5' end of a pre-existing strand
B)it can only replicate the leading strand
C)it can only replicate the lagging strand
D)all of the above
E)none of the above

2The enzyme ________ unzips and unwinds the DNA molecule.
A)DNA polymerase
D)DNA ligase

3Which of the following statements about DNA replication is TRUE?
A)the leading strand is replicated continuously, while the lagging strand is replicated discontinuously
B)the leading strand is replicated discontinuously, while the lagging strand is replicated continuously
C)both the leading and lagging strands are replicated continuously
D)both the leading and lagging strands are replicated discontinuously
E)each of the leading and lagging strands is replicated both continuously and discontinuously

4DNA replication results in two identical daughter molecules each consisting of one old (original) strand and one newly-synthesized strand.

5The point where separation of the DNA occurs is called the replication fork.

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