PCR

Why replicate DNA sections?

Insulin
Favourable DNA
Forensics for analysis

PCR = Polymerase chain reaction

PCR

A technique that amplifies DNA allowing you to increase the amount of DNA from a small sample. It's important as it has many applications: forensics, genetic diseases, monitoring disease spread.

How does it work?

Artificial replication of DNA
Cyclic reaction

Needs:

DNA samples
DNA polymerase
Excess A, T, G, C
Primer - 3/4 base pairs long. Starts a bit of the double-strand, Allows DNA polymerase to work as doesn't work on single strands.
Thermal cycler

3 stages:

Denaturing - Heat DNA sample to 94-96 degrees to break hydrogen bonds. The whole strand unzips in denaturing.
Annealing - Cool to 68 degrees. This allows the primer to hydrogen bonds creating 1st new double-stranded DNA section.
Extending - Heat to 72 degrees, DNA polymerase binds to end and catalysts addition of nucleotides.

Uses of PCR:

Tissue typing
Detection of oncogenes (cancer genes)
Detecting mutations, e.g. Down syndrome
Identifying viral infections
Monitoring spread of infectious disease
Forensic science
Research
Detect ancient DNA
Cloning
Identifying transgenic plants