Nematodes

Gel electrophoresis

    Gel electrophoresis is a technique used in molecular biology to separate charge bearing polymers (proteins, RNA, or DNA) under the influence of the electric field in a semisolid medium called gel made of agar, agarose, or polyacrylamide. The molecules being stored are dispensed into a well in the gel material. The gel is placed in an electrophoresis chamber, which is then connected to a power source. When the electric current is applied, the different sized molecules begin to move to the opposite pole through the gel.

Principle of movement in the gel

    The movement of the fragment is primarily dependent upon size because the distance, a DNA fragment travels, is inversely proportional to its length so the smaller fragments move faster through the gel matrix than larger fragments. However, the movement of the fragments also depends upon charges, number of strands (single or double), and shape of the molecules (linear or circular), and the concentration of the gel (pore size). Therefore, after sometimes the different sized molecules have been separated into distinct bands on the gel.

Visualization of fragments

    To visualize DNA or RNA, the gel is placed on an ultraviolet transilluminator. Now you can observe that some bands are thick and some are thin. Thick bands represent the high concentration of same sized fragments while thin bands show low concentration.
    If a particular sized fragment is to be used for further analysis, the piece of the gel containing that band can be cut and its DNA can be purified again. DNA bands can also be transferred from gel to the nitrocellulose membrane for autoradiography (X-ray imaging). Be aware that DNA will diffuse within the gel over time, and examination or photography should take place shortly after cessation of electrophoresis.