What is the purpose of a a “no dna” control reaction? what does it mean if the gel lane has bands?

The purpose of a 'no DNA' control reaction or negative-control reaction would be to know the protein level backgrounds (flourescence & endogenous biotinylated proteins) in the sample. If the gel lane has bands, it means that DNA is present. 

1) clean up you lab area2) dispose of the chemicals as instructed by your teacher3) put everything back where it belongs unless your teacher tells you otherwise4) dispose of gloves5) wash hands with soap and water