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Lac Operon - I gene

In the table below, predict (yes or no) whether or not the E. coli lac operon will be transcriptionally active in the presence or absence of glucose or lactose as indicated and respond
Lactose Glucose Lac expression?
No Yes
Yes Yes
Yes No
to questions "a" and "b."

a. Explain each of your answers in terms of the molecular mechanisms that are known to underlie the regulation of the lac operon.

b. Which mechanism is considered to be negative control and which is considered to be positive control? Explain.

Solution Preview

lactose glucose
In the table below, predict (yes or no) whether or not the E. coli lac operon will be transcriptionally active in the presence or absence of glucose or lactose as indicated and respond
Lactose Glucose Lac expression?
No Yes
Yes Yes
Yes No
to questions "a" and "b."

a. Explain each of your answers in terms of the molecular mechanisms that are known to underlie the regulation of the lac operon.

b. Which mechanism is considered to be negative control and which is considered to be positive control? Explain.

Table 1:

Lactose Glucose Lac expression

No Yes No

Yes Yes No
Yes No Yes

a. Explain each of your answers in terms of the molecular mechanisms that are known to underlie the regulation of the lac operon.

I P O || Z | Y | A ...

Solution Summary

The lactose operon contain the I gene that encode for the repressor; the P gene that encode for the promoter; the O gene that encode the operator. The structural genes Z Y A downstream of the operator. The Z gene encode the B-Galactosidase; the Y gene encode the Permease; and the A gene that encode the Transacetylase.

B-galactosidase - converts lactose into glucose and galactose
B-galactoside permease - transports lactose into the cell
B-galactoside transacetylase- unknown function

The lac operon function as both a negative and positive regulation of the degradation of lactose. It is an inducible system that depends on the presence of the inducer lactose.

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