Question

Why does the lac operon shut down some time after the addition of lactose in the medium
where E.coli was growing? Why low level expression of lac operon is always required?

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Answer 1

Operon

Small amounts of allolactose are formed when lactose enters E. coli. Allolactose binds to an allosteric site on the repressor protein causing a conformational change. As a result of this change, the repressor can no longer bind to the operator region and falls off.

The function of lac operon is to codes for proteins required to transport lactose into the cell and to break it down. ... The lac repressor so ensures that the lac operon is shut off in the absence of lactose.

Answer 2

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kashu77

Secondary School Biology 5+3 pts

Why does the Lac Operon shut down sometimes after the addition of lactose in the medium where E coli was growing ? why low level expression of Lac Operon is always required ?

Report by Pallavisingh1664 09.11.2018

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thewordlycreature

Thewordlycreature Virtuoso

The function of lac operon is to codes for proteins required to transport lactose into the cell and to break it down. CAP helps bacteria to use alternative carbon sources in the absence of glucose. The lac repressor so ensures that the lac operon is shut off in the absence of lactose. This arrangement helps the control region of lac operon to respond to and integrate two different signals.

i. lactose must be present

ii. glucose must be absent

Any of the other three possible signal combinational maintains the group of genes in the off state.

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Topanswers Samaritan

The Lactose Operon or Lac Operon is a basic and fundamental component in the DNA structure of E.coli bacteria. It supports the metabolic activity of lactose and its movement.

Presence of lactose in the medium of the E.coli growth stops the binding of the repressor to operon, allowing the polymerase to bind with the operon and perform the genetic transcription .

Later, when the cells utilize entire content of the lactose present, repressor becomes bond free. Now, it binds to the operon and inhibits the transcription process. Finally, the operon shuts down.

It is possible for bacterial cells to use lactose in the medium, only if there is availability of permease in the bacteria. Permease can be formed only when there is low level expression of the Lac Operon.

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