M. luteus can be found in many places such as the human skin, water, dust, and soil. Micrococcus is generally thought of as harmless bacterium, but there have been rare cases of Micrococcus infections in people with compromised immune systems, as occurs with HIV patients.
Therefore when used in gel electrophoresis, markers effectively provide a logarithmic scale by which to estimate the size of the other fragments (providing the fragment sizes of the marker are known). Protein, DNA, and RNA markers with pre-determined fragment sizes and concentrations are commercially available.
Gel electrophoresis is used to separate things (DNA, RNA, or proteins) by their size. Gel electrophoresis is used to separate things (DNA, RNA, or proteins) by their size. For example, say you have a sample of protein that you have prepared accordingly and want to separate by size. You would run it through a gel, and after a designated amount of time, would view the progress that the protein has made through the gel, and then image the gel.