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Ch. 18 - Control of Gene Expression in Bacteria
Freeman - Biological Science 8th Edition
Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook
All textbooksFreeman 8th EditionCh. 18 - Control of Gene Expression in BacteriaProblem 4
Chapter 18, Problem 4

A regulon is a set of genes controlled by
a. One type of regulator of transcription
b. Two or more different alternative sigma proteins
c. Many different types of promoters
d. Glucose

Verified step by step guidance
1
Understand the term 'regulon': A regulon is a group of genes or operons that are regulated together by a single regulatory protein or mechanism, often in response to specific environmental or cellular signals.
Analyze option (a): 'One type of regulator of transcription.' This aligns with the definition of a regulon, as it typically involves a single regulatory protein controlling multiple genes.
Evaluate option (b): 'Two or more different alternative sigma proteins.' Sigma proteins are involved in transcription initiation, but a regulon is not defined by multiple sigma proteins. This option is not correct.
Evaluate option (c): 'Many different types of promoters.' Promoters are sequences where RNA polymerase binds to initiate transcription, but a regulon is defined by shared regulation, not by the diversity of promoters. This option is not correct.
Evaluate option (d): 'Glucose.' Glucose is a molecule involved in metabolism and does not directly define a regulon. This option is not correct.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Regulon

A regulon is a collection of genes that are regulated together, typically by a single regulatory protein or a set of related proteins. These genes often share a common function or are involved in a specific metabolic pathway. Understanding regulons is crucial for grasping how cells coordinate gene expression in response to environmental changes.

Transcription Regulation

Transcription regulation refers to the mechanisms that control the transcription of genes, determining when and how much of a gene product is made. This process can involve various factors, including transcription factors, enhancers, and repressors, which interact with DNA to modulate gene expression. It is essential for cellular responses to stimuli and maintaining homeostasis.
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Sigma Factors

Sigma factors are proteins that bind to RNA polymerase and direct it to specific promoters, initiating transcription in bacteria. Different sigma factors recognize different sets of promoters, allowing the cell to respond to various environmental conditions by activating or repressing groups of genes. Understanding sigma factors is key to comprehending how bacteria adapt to changes in their environment.
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Related Practice
Textbook Question

Why are the genes involved in lactose metabolism considered to be an operon?

a. They occupy adjacent locations on the E. coli chromosome.

b. They have a similar function.

c. They are all required for normal cell function.

d. They are all controlled by the same promoter.

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Textbook Question

In the lac operon, the repressor inhibits transcription when

a. The repressor is bound to the inducer.

b. The repressor is not bound to the inducer.

c. The repressor is bound to glucose.

d. The repressor is not bound to the operator.

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Textbook Question

Activators bind to regulatory sequences in ________ and to ________ polymerase.

Textbook Question

Evaluate these statements about regulation of the lac operon. Select True or False for each statement.

T/FThe lac operon is transcribed at the highest rate when extracellular glucose and lactose are abundant.

T/FThe repressor protein is bound to DNA of the operator when lactose is present.

T/FA mutation in the operator is likely to prevent transcription of the lac operon under any condition.

T/FA mutation that alters the catabolite activator protein is predicted to alter the regulation of many different operons.

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Textbook Question

Predict what would happen to regulation of the lac operon if the lacI gene were moved 50,000 nucleotides upstream of its normal location.

Textbook Question

Explain why it makes sense for the lexA regulatory gene of the SOS regulon to be expressed constitutively.