4.4.2 Gel Electrophoresis
4.4.2 State that, in gel electrophoresis, fragments of DNA move in an electric field and are separated according to their size. In Gel Electrophoresis the DNA is placed in wells at one end of the agarose gel. The wells are labelled according whether they contain a 'Standard' (DNA fragments of known size) and a crime scene (CS) with suspects (1, 2 etc) for example. The Agarose gel is then put into an electrophoresis chamber with the DNA samples closest the to negative pole. This is because DNA as a molecule is slightly negatively charged and therefore will move towards the positive pole when placed in an electric field. The samples are separated by size with the largest DNA fragments remaining closest to the wells and the smallest DNA fragments migrating furthest away from the wells.