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.'