The “PaJaMo” experiment of PArdee, JAcob, and MOnod “broke the impasse in Crick and Brenner’s comprehension of how information in the sequence of bases in DNA came to be expressed as a sequence of the amino acids in protein, and thus led to the theory of the messenger and the solution of the coding problem” (Judson 390).

This was recorded definitively in “The Genetic Control and Cytoplasmic Expression of ‘Inducibility’ in the Synthesis of β-galactosidase by E. coli,” J. Mol. Biol. 1 (1959) 165-78.

Jacob and Monod received their share of the Nobel Prize in 1965 for their discoveries concerning the operon and viral synthesis. The first operon they described was the lac operon in E. coli. Their operon theory suggested that in all cases, genes within an operon are negatively controlled by a repressor acting at a single operator located before the first gene. Later, it was discovered that genes could be positively regulated, and also regulated at steps that follow transcription initiation. Therefore, no generalized regulatory mechanism is possible because different operons have different mechanisms. Today, an operon is defined as a functioning unit of DNA containing a cluster of genes under the control of a single promotor, transcribed together into a single mRNA strand. 

Jacob, Monod, and André Lwoff shared the Nobel Prize in 1965 for their discovery of a gene whose function is to regulate the activity of other genes.