Page 17 - An Identity Crisis
P. 17
Three Stages of PCR:
PCR is conducted in commercially available 2. ANNEALING: Temperatures between 50°C
instruments, called thermal cyclers, that heat and to 65°C. The primers bind to the DNA outside
cool the tubes that contain the reaction components. the targeted region (the region to be amplified)
Three steps are repeated approximately 30 times by forming hydrogen bonds with the specific
(called cycles), which results in the replication of complementary sequences flanking the target
billions of copies of the targeted DNA sequence. region, thus defining the sequence to be copied.
3. EXTENSION (ELONGATION): Temperature of
1. DENATURATION: Temperature greater than approximately 72°C. Taq polymerase is activated
90°C. The hydrogen bonds of the doublestranded and incorporates the free dNTPs into the area
DNA ladder are broken, allowing the two strands between the primers.
to separate.
THE MYSTERY OF LYLE AND LOUISE 17
