After completion of the electrophoresis of DNA fragments along with the proper molecular-weight standard on an agarose gel, suppose (a) or (b) below was observed.
What might be explanations for these?
a. The gel is blank (no bands, no molecular-weightstandard).
b. Only the molecular weight standard is visible.
a. Since the molecular-weight standard is not visible, something is wrong with the general electrophoresis process. Most likely, staining with ethidium bromide was omitted.
b. The presence of the molecular-weight standardindicates that the electrophoresis and staining were performed properly. In this case, the DNA fragments were not loaded, or the method used to produce the fragments was unsucessful.