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

PCR and Electrophoresis