the first question...
lac operon is regulated by a specific protein called lactose.
the second question....
the eukaryotic genes are controlled by the lactose proteins binding to the regulatory sites through the regulatory surface.
the third question....
DIFFERENCE:prokaryotes regulation occurs in the cytoplasm while eukaryotes regulation occurs in the nucleus..
SIMILARITY:The transcription level of prokaryotes occurs in the cytoplasm and also the protein transcription level of the eukaryotes occurs in the cytoplasm