Question

Explain whether the results on the effect of lactose reflect an adaptive mechanism of gene regulation. Does it make biological sense for lactose to have this effect? Why? Is it adaptive for glucose to alter the ability of lactose to induce the enzymes needed for lactose breakdown? Explain.

Answer 1

Yes, results on the effect of lactose (lac) shows adaptive mechanism of gene regulation. Generally, bacteria persists adaptive mechanism of gene regulation for most of the proteins. Responce of the bacteria in term of gene expression to the change in environment is called as adaptive gene regulation.

In lac operon, the expression of gene involved in lactose break down (structural genes) are regulated by the availability of lactose in the environment. It also have biological sense, because bacteria need to invest its energy in the expression of lac structural genes. In the absence of lactose, their presence will not play any role in bacteria and therefore their expression will be wastage.

No, it is not adaptive for the glucose, because degradation of lactose will produce glucose and galactose. And hence cell can utilized the glucose for its metabolism. However, but if the lactose is absent in the medium then one may say it is adaptive because cell will not waste its energy in the production of lac structural genes because in the presence of glucose, cAMP will not available for the activation of lactose operon.

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