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Chapter 18: Q18.1-2CC. (page 368)

Describe the binding of RNA polymerase, repressors, and activators to the lac operon when both lactose and glucose are scarce. What is the effect of these scarcities on transcription of the lac operon?

Short Answer

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RNA polymerase is the enzyme that mediates the process of transcription of a gene. The cAMP binds to the receptor protein called cAMP receptor protein. During the absence of glucose, this complex binds with the lac operon. It activates the transcription of the lac operon.

The absence of lactose can block the transcription process due to the binding of the repressor to the lac operator.

Step by step solution

01

Description of activators and repressors

The activators are the molecules that trigger the transcription process in a particular gene. The repressor is the molecules that block the transcription of a specific gene.

02

Step 2: Description of RNA polymerase

RNA polymerase is the enzyme that acts on the DNA molecule and converts the DNA into RNA. Prokaryote has a polymerase with the catalytic core along with the other subunits. Mainly, the RNA polymerase binds to the promoter region of the RNA polymerase.

03

Effect of the scarcity of glucose and lactose in the lac operon

Lac operon helps the cell to metabolize the lactose that is consumed. The operon contains the gene coding for the enzyme beta-galactosidase. The presence of substrates such as lactose and glucose makes the digestion process of lactose easier.

During the absence of glucose, cAMP will bind to the CRP, activating the lac operon since CAMP acts as a substitute for glucose.

In the absence of lactose, the lac operator is blocked by the lac repressor that stops the transcription process.

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