This tutorial gives details of how genes can be regulated in eukaryote and prokaryotes. It explains the two operons and their use to bacterias. Transcription factors and their importance in eukaryote s is also discussed Paul Andersen explains how genes are regulated in both prokaryotes and eukaryotes. He begins with a description of the lac and trp operon and how they are used by bacteria in both positive and negative response. He also explains the importance of transcription factors in eukaryotic gene expression.