P1

FIGURE 23.27 Rolling Circle Amplification of DNA—Exponential Version

As in the linear version, E-RCAT reactions start with polymerase and the first primer (P1). Rolling circle replication produces tandem single-stranded copies of the circular target DNA. Next, a second primer (P2) anneals at the end of each tandem segment. Complementary strands of DNA are then synthesized starting from primer P2, which makes the entire DNA region double-stranded. As the DNA polymerase passes the end of a target segment, it displaces the DNA strand in front of it, making a single-stranded branch. The first primer, P1, can anneal to the inside end of the branch and polymerase makes the second strand.

New DNA from P2

New DNA from P2

Branching

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