Gel Electrophoresis

Marker DNA

A series of molecular fragments of known size, used to determine the size of the other fragments by comparison

Southern Blotting

An alternative technique where a sheet of nylon or nitrocellulose is placed over the gel and the DNA fragments stick to the sheet, forming a DNA profile

Method

An electric current is applied across the gel so that one end of the gel has a positive charge and the other end has a negative charge. DNA is negatively charged, therefore, when an electric current is applied to the gel, DNA will migrate towards the positively charged electrode. Shorter strands of DNA move more quickly through the gel than longer strands resulting in the fragments being arranged in order of size.

Agarose

The gel (from seaweed) used in gel electrophoresis

Gel Electrophoresis

a technique commonly used in the lab to separate charged molecules, like DNA, RNA and proteins, according to size when they move through a gel when an electric current is passed across it.

Fluorescent Dyes

enables the DNA on the gel to be seen after they have been separated by bonding with the DNA. They will appear as bands on the gel under ultraviolet radiation

DNA

negatively charged due to the presence of phosphate groups

Smaller Molecules

travel at a greater rate towards the positive charge because their molecular weight is less

Larger molecules

travel at a slower rate and stay closer to the negative charge because they have a greater molecular weight