Bacterial genomes frequently contain groups of genes organized into operons. What is the biological advantage of operons to bacteria? Identify the regulatory components you would expect to find in an operon. How are the expressed genes of an operon usually arranged?

Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following:

Operator

Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following:

Repressor

Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following:

Inducer

Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following:

Corepressor

Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following:

Promoter

Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following:

Positive regulation

Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following:

Allostery

Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following:

Negative regulation

Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following:

Attenuation

Identify similarities and differences between an inducible operon and a repressible operon in terms of

The transcription-regulating DNA sequences.

Identify similarities and differences between an inducible operon and a repressible operon in terms of

The presence and action of allosteric regulatory molecules.

Identify similarities and differences between an inducible operon and a repressible operon in terms of

The organization of structural genes of the operon.

The transcription of -galactosidase and permease is inducible in lac⁺ bacteria with a wild-type lac operon. Explain the mechanism by which lactose gains access to the cell to induce transcription of the genes.

Is attenuation the product of an allosteric effect? Is attenuation the result of a transcriptional or a translational activity? Explain your answers.

The trpL region contains four repeated DNA sequences that lead to the formation of stem-loop structures in mRNA. What are these stem-loop structures, and how do they affect transcription of the structural genes of the trp operon?

The CAP binding site in the lac promoter is the location of positive regulation of gene expression for the operon. Identify what binds at this site to produce positive regulation, under what circumstances binding occurs, and how binding exerts a positive effect.

What role does cAMP play in transcription of lac operon genes? What role does CAP play in transcription of lac operon genes?

How would a cap⁻ mutation that produces an inactive CAP protein affect transcriptional control of the lac operon?

Explain the circumstances under which attenuation of operon gene expression is advantageous to a bacterial organism. Would you expect attenuation to be found in a single-celled eukaryote? In a multicelled eukaryote?

Consider the transcription of genes of the lac operon under two conditions: (1) when both glucose and lactose are present and (2) when glucose is absent and lactose is present. Describe the comparative levels of transcription of lac operon genes under these conditions, and explain the molecular basis for the difference.

Describe the lytic and lysogenic life cycles of λ bacteriophage. What roles do λ repressor and Cro protein play in controlling transcription from P_R and P_RM, and how are these roles linked to lysis and lysogeny?

Define antisense RNA, and describe how it affects the translation of a complementary mRNA. Why is it more advantageous to the organism to stop translation initiation than to inactivate or destroy the gene product after it is produced?

Attenuation of trp operon transcription is controlled by the formation of stem-loop structures in mRNA. The attenuation function can be disrupted by mutations that alter the sequence of repeat DNA regions 1 to 4 and prevent the formation of mRNA stem loops. Describe the likely effects on attenuation of each of the following mutations under the conditions specified.

In the lac operon, what are the likely effects on operon gene transcription of the mutations described in a–e?

Mutation of consensus sequence in the lac promoter

In the lac operon, what are the likely effects on operon gene transcription of the mutations described in a–e?

Mutation of the repressor binding site on the operator sequence

In the lac operon, what are the likely effects on operon gene transcription of the mutations described in a–e?

Mutation of the lacI gene affecting the allosteric site of the protein

In the lac operon, what are the likely effects on operon gene transcription of the mutations described in a–e?

Mutation of the lacI gene affecting the DNA-binding site of the protein

In the lac operon, what are the likely effects on operon gene transcription of the mutations described in a–e?

Mutation of the CAP binding site of the lac promoter