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lac and trp Operon

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Questions and Answers

Which of the following is true about the lac operon?

It is found in viruses

It controls the metabolism of lactose in bacteria (correct)

It consists of four main structural genes

It encodes proteins involved in glucose metabolism

What is the role of lacZ in the lac operon?

Encodes lactose permease, a membrane protein that transports lactose into the cell

Acts as a DNA sequence where RNA polymerase binds to initiate transcription

Encodes transacetylase, which is involved in lactose metabolism

Encodes β-galactosidase, which breaks down lactose into glucose and galactose (correct)

Where is the operator located in the lac operon?

Before the promoter

Outside of the lac operon

After the structural genes

Between the promoter and the structural genes (correct)

What is the main function of the lac operon?

To control the metabolism of lactose Signup and view all the answers

Which bacteria is the lac operon found in?

Escherichia coli (E. coli) Signup and view all the answers

What is the function of the lac repressor protein in the absence of lactose?

It prevents RNA polymerase from transcribing the structural genes. Signup and view all the answers

Which molecule acts as an inducer in the lac operon?

Allolactose Signup and view all the answers

What is the main function of the trp operon?

To regulate the biosynthesis of tryptophan Signup and view all the answers

Which component of the trp operon acts as a regulatory region where a repressor protein can bind to control gene expression?

Operator Signup and view all the answers

What happens to the trp repressor protein in the presence of tryptophan?

It becomes inactive and cannot bind to the operator. Signup and view all the answers

Study Notes

The lac operon and trp operon are two significant operons in bacteria, located in E. coli.
The lac operon manages lactose metabolism, whereas the trp operon oversees tryptophan biosynthesis.
The lac operon includes the structural genes lacZ, lacY, and lacA, which encode proteins involved in lactose metabolism, a promoter, and an operator.
lacZ encodes β-galactosidase
lacY encodes lactose permease
lacA encodes transacetylase
Regulation of the lac operon occurs via the presence or absence of lactose and glucose.
Lac repressor binds to the operator when lactose is absent, preventing transcription.
Allolactose, derived from lactose, serves as an inducer, changing the lac repressor's conformation and releasing it from the operator to enable transcription.
The trp operon consists of the structural genes trpE, trpD, trpC, trpB, and trpA, a promoter, an operator, and regulates tryptophan biosynthesis.
Regulation of the trp operon hinges on the availability of tryptophan.
Trp repressor is inactive without tryptophan, allowing transcription.
Tryptophan acts as a corepressor when present, binding to the trp repressor and altering its conformation, preventing transcription.

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Description

Learn about the lac operon and trp operon, two essential operons in E. coli bacteria. Understand the functions of the structural genes, the regulatory mechanisms, and the role of inducers and corepressors in gene expression.