Steps in PCRcontinued
Molecular Diagnostics
(MDx) Review 557
STEP TEMP/TIME* EXPLANATION
- Extension (polymerization)
Cycle repeated 15–40 times*Exact temperatures & times vary.
DNA polymerase attaches to ends of primers, adds dNTPs that are
complementary to template, synthesizing new strands of DNA.Each cycle results in doubling of DNA, yielding millions of copies of original
DNA segment. Amplicon can be analyzed by variety of methods, e.g., gel
electrophoresis, hybridization.68 °–75°C/
10–60 sec.3 ¢3 ¢DNA
5 ¢5 ¢(From Buckingham L. Molecular Diagnostics: Fundamentals, Methods, and
Clinical Applications, 2nd ed. Philadelphia: FA Davis; 2012:134.)