Operons are groups of genes clustered in the bacterial DNA regulating the expression of functionally related proteins. In E. coli half of the genes are clustered into operons which are involved in particular metabolic pathways. Lac operon model was proposed by Jacob & Monad. Lac Operon is responsible for the transport and metabolism of lactose. Got something to say about this post? Leave a comment...your comments are valuable for improving the posts.