Polymerase Chain Reaction (PCR) allows scientists to make millions of copies of a specific DNA sequence starting with only a small sample. PCR involves repeated cycles of heating and cooling DNA to separate the strands and allow new strands to be synthesized using DNA polymerase. Kary Mullis invented PCR in 1983 while working at Cetus Corporation, and it has since become a fundamental technique for amplifying DNA sequences, enabling applications like DNA fingerprinting using very small forensic samples.

1. Polymerase Chain Reaction “Xeroxing” DNA

5. PCR: Amplification of DNA

7. PCR basis: Directionality of DNA backbone

8. Recall that DNA is antiparallel

9. Heat causes denaturing—H-bonds between base pairs “break”

12. Note: SYNTHESIS occurs in the 5’  3’ direction

14. Old Faithful!

20. PCR: Pipetting the reagents into the reaction tube

36. After 30 cycles this becomes one billion! 2 30