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Gel electrophoresis

Gel electrophoresis sorts DNA fragments by size. The gel is a mesh, and DNA is negatively charged, so the fragments are pulled towards plus. Small fragments slip most easily through the mesh and travel furthest. Large fragments are held back. You compare with fragments of known length that were placed in a neighbouring well. The method does not say what the sequence is, only how long the fragments are. Together with restriction enzymes it gives a pattern, a DNA profile. Identical twins have the same profile. Other people do not.

short fragment→furthest travel\text{short fragment} \rightarrow \text{furthest travel}sorting in the gel

Symbols

DNADNAnegative charge
gelgelmesh that slows large fragments

Example

The smallest fragments travel furthest.

The largest stay closest to the well.

PCR copies, the enzyme cuts, the gel sorts. The three do different jobs.
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← Restriction enzyme · Resting potential →

Part of Biology 2: Biotechnology.