Answer:
Contamination of a sample
Step-by-step explanation:
Gel electrophoresis is a method used in molecular biology for DNA analysis. This method includes the separation of DNA fragments through the gel according to their size or shape.
One of the major source of error is contamination of the DNA sample. This refers to the presence of foreign DNA in the sample of interest. As a consequence, the gel will have more bands.
Another errors might appear as a result of wrong concentration of the gel, wrong buffer pH, high/low concentration of dye etc.