For the polymerase chain reaction to occur,
A) isolated DNA molecules must be primed.
B) all DNA fragments must be identical.
C) the DNA must remain double stranded.
D) a sticky end must be available for the ligase enzyme to function.
E) all of these must occur.

Question

Quizplus · Accepted Answer

Isolated DNA molecules must be primed in order for the polymerase chain reaction to occur. Primers are short, single-stranded DNA molecules that serve as starting points for DNA synthesis by PCR. Without primers, the DNA polymerase used in PCR would have nowhere to start replicating the target DNA sequence. Choices B, C, and D are incorrect because PCR can be used to amplify a wide variety of DNA fragments, including those that are not identical, those that are single-stranded, and those that do not have sticky ends.

For the Polymerase Chain Reaction to Occur