Lac Operon - Development of The Classic Model

Development of The Classic Model

The experimental microorganism used by François Jacob and Jacques Monod was the common laboratory bacterium, E. coli, but many of the basic regulatory concepts that were discovered by Jacob and Monod are fundamental to cellular regulation in all organisms. The key idea is that proteins are not synthesized when they are not needed--- E. coli conserves cellular resources and energy by not making the three Lac proteins when there is no need to metabolize lactose, such as when other sugars like glucose are available. The following section discusses how E. coli controls certain genes in response to metabolic needs.

During World War II, Monod was testing the effects of combinations of sugars as nutrient sources for E. coli and B. subtilis. Monod was following up on similar studies that had been conducted by other scientists with bacteria and yeast. He found that bacteria grown with two different sugars often displayed two phases of growth. For example, if glucose and lactose were both provided, glucose was metabolized first (growth phase I, see Figure 2) and then lactose (growth phase II). Lactose was not metabolized during the first part of the diauxic growth curve because β-galactosidase was not made when both glucose and lactose were present in the medium. Monod named this phenomenon diauxie.

Monod then focused his attention on the induction of β-galactosidase formation that occurred when lactose was the sole sugar in the culture medium.

Read more about this topic:  Lac Operon

Famous quotes containing the words development of the, development of, development, classic and/or model:

    Women, because of their colonial relationship to men, have to fight for their own independence. This fight for our own independence will lead to the growth and development of the revolutionary movement in this country. Only the independent woman can be truly effective in the larger revolutionary struggle.
    Women’s Liberation Workshop, Students for a Democratic Society, Radical political/social activist organization. “Liberation of Women,” in New Left Notes (July 10, 1967)

    Women, because of their colonial relationship to men, have to fight for their own independence. This fight for our own independence will lead to the growth and development of the revolutionary movement in this country. Only the independent woman can be truly effective in the larger revolutionary struggle.
    Women’s Liberation Workshop, Students for a Democratic Society, Radical political/social activist organization. “Liberation of Women,” in New Left Notes (July 10, 1967)

    Ultimately, it is the receiving of the child and hearing what he or she has to say that develops the child’s mind and personhood.... Parents who enter into a dialogue with their children, who draw out and respect their opinions, are more likely to have children whose intellectual and ethical development proceeds rapidly and surely.
    Mary Field Belenky (20th century)

    One classic American landscape haunts all of American literature. It is a picture of Eden, perceived at the instant of history when corruption has just begun to set in. The serpent has shown his scaly head in the undergrowth. The apple gleams on the tree. The old drama of the Fall is ready to start all over again.
    Jonathan Raban (b. 1942)

    The Battle of Waterloo is a work of art with tension and drama with its unceasing change from hope to fear and back again, change which suddenly dissolves into a moment of extreme catastrophe, a model tragedy because the fate of Europe was determined within this individual fate.
    Stefan Zweig (18811942)