Why use a negative control when running gel electrophoresis? if a band shows up in this lane, what does it tell you about your pcr products?

Ans.

Gel electrophoresis is a molecular biology technique, used in the separation of proteins and nucleic acid molecules. When gel electrophoresis is performed, a negative control is used along with a positive control during PCR to detect presence of any possible contamination.

In negative control lane, no band is expected as it is considered as blank. Thus, 'a band in the lane of negative control shows presence of some sort of contaminating molecules in the amplified sample DNA.'