What is an operon and what does it do?

What is an operon and what does it do?

Operon, genetic regulatory system found in bacteria and their viruses in which genes coding for functionally related proteins are clustered along the DNA. This feature allows protein synthesis to be controlled coordinately in response to the needs of the cell.

What is the lac operon and why is it important?

The classic example of prokaryotic gene regulation is that of the lac operon. This operon is a genetic unit that produces the enzymes necessary for the digestion of lactose (Fig. 16-13). The lac operon consists of three contiguous structural genes that are transcribed as continuous mRNA by RNA polymerase.

How is the lac operon controlled?

Regulation of the lac Operon The activity of the promoter that controls the expression of the lac operon is regulated by two different proteins. One of the proteins prevents the RNA polymerase from transcribing (negative control), the other enhances the binding of RNA polymerase to the promoter (positive control).

What is lac Z?

The gene product of lacZ is β-galactosidase which cleaves lactose, a disaccharide, into glucose and galactose. lacY encodes Beta-galactoside permease, a membrane protein which becomes embedded in the cytoplasmic membrane to enable the cellular transport of lactose into the cell.

How does glucose affect the lac operon?

The lac operon has an added level of control so that the operon remains inactive in the presence of glucose even if lactose also is present. High concentrations of glucose catabolites produce low concentrations of cAMP, which must form a complex with CAP to permit the induction of the lac operon.

How long the lac operon would be expressed in the presence of lactose?

The Lactose operon expresses as long as the Lactose is present. When all lactose is converted into glucose and galactose, the reaction stops.

Which of the following is false about the E coli lac operon?

8. According to the repressor of lac operon which of the following are false? Explanation: The repressor of the lac operon does not bind to the promoter region. It binds to the operator region of the lac operon thus repressing the activity of the lac operon.

How is the lac operon affected by negative control?

Explanation: The lac operon exhibits both systems. It is a negative control system because expression is typically blocked by an active repressor (the lac repressor) that turns off transcription. The lac repressor binds to the operator region and negatively controls (prevents) transcription.

How is the lac operon affected by negative control quizlet?

lac operon is under negative control by a repressor protein (because once bound the lac repressor prevents RNA polymerase from transcribing the lacZ, lacY, and lacA genes. lac operon is under positive control by an activator protein, the catabolite activator protein (CAP).

Which is an example of negative regulation?

Repressor binding blocks RNA polymerase from binding with the promoter, thereby leading to repression of operon gene expression. A classic example of negative repressible regulation of gene expression involves the trp operon, which is regulated by a negative feedback loop.

How is the expression of lac operon genes affected by negative control quizlet?

How is the lac operon affected by negative control? In both the lac and trip operons of E. coli, a repressor binds to an operator to block transcription.

Which of the following is a major difference between different DNA binding motifs?

Which of the following is a major difference between different DNA-binding motifs? They employ different mechanisms to position and stabilize a recognition alpha helix in the major groove of DNA.

How does glucose affect the lac operon quizlet?

How does glucose affect the lac operon? When glucose levels are low, cAMP levels are high. cAMP binds to and activates the CAP protein, allowing it to bind to the DNA.

What are the main steps of gene regulation in eukaryotic cells in the correct order?

Stages of eukaryotic gene expression (any of which can be potentially regulated).

• Chromatin structure. Chromatin may be tightly compacted or loose and open.
• Transcription.
• Processing and export.
• mRNA stability.
• Translation.
• Protein processing.

What are 2 ways in which eukaryotic cells regulate gene expression?

Eukaryotic gene expression is regulated during transcription and RNA processing, which take place in the nucleus, and during protein translation, which takes place in the cytoplasm. Further regulation may occur through post-translational modifications of proteins.