Question

A functional complex comprising a cluster of genes including structural gene, a promoter gene, an operator gene and a regulator gene was discovered by

• A. Beadle and Tatum (1958)
• B. Watson and crick (1953)
• C. Jacob and Monod (1961)
• D. Britten and Davidson (1961)

Answer 1

Answer: (C)

Jacob and Monod (1961)

The lac operon is an operon responsible for transport and metabolism of lactose in Escherichia coli and other bacteria. The mechanisms of regulation of expression of genes responsible for coding the involved enzymes was first explained by Francois Jacob and Jacque Monod while working on inducible system for synthesis of $\beta$-galactosidase enzyme in E. coli. According to the model, an operon cosists of operator gene and structural genes. The operator gene regulates the expression of structural genes by providing a binding site to transcription factor which in turn regulate the gene expression by altering the binding of RNA polymerase to the promoter region. The regulator genes code for transcription factor/repressor proteins that binds to operators or promoters and prevent RNA polymerase from transcribing RNA. The alteration in repressor proteins by inducers make them unable to bind DNA and allow RNA polymerase to carry out transcription. Option C is correct answer.