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Structure
Operons comprise three main parts: the promoter, operator and genes. The promoter is a part of the DNA that helps genes be transcribed, or copied; this copy is called RNA -- ribonucleic acid -- and it is the DNA's messenger that tells the prokaryote what to do. The operator lies between genes and the promoter; it activates the RNA when genes are ready to be transcribed. Genes are regulated by the operon.
Lac Operon
The lac operon is one of the most commonly studied operons. Discovered in the prokaryote known as E. coli, the lac operon's cluster of three genes allows E. Coli to metabolize glucose, its favorite food. However, E. Coli also consumes lactose, and for it to efficiently metabolize glucose, its lactose-metabolizing mechanism must be blocked. The lac operon takes care of this, blocking lactose metabolisis so the E. coli can receive its glucose.
Trp Operon
The trp operon does the opposite function of the lac operon. Whereas the lac operon turns on E. coli's ability to metabolize something, the trp operon turns that ability off. The trp operon is named for the amino acid tryptophan, which is required by all organisms to live. When the E. coli or other prokaryote has enough tryptophan, the trp operon tells the cell to stop synthesizing tryptophan until more is needed.
Pascale Cossart and Listeria
In 2009, bacteriologist Pascale Cossart published the first complete map of an operon, laying out genetic switches that work together to operate listeria, a food-borne pathogen. Cossart's operon-related inquiry into the bacteria helped show how its genes and proteins collaborate to help this bacteria work its way into blood cells and other vulnerable areas in humans and animals. Her work gave hope to those seeking a cure for food-borne pathogens at large.