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Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoSanders 3rd EditionCh. 12 - Regulation of Gene Expression in Bacteria and BacteriophageProblema 28a
Capitolo 12, Problema 28a

How would mutations that inactivate each of the following genes affect the determination of the lytic or lysogenic life cycle in mutated λ phage strains? Explain your answers.
cI

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Understand the role of the cI gene: The cI gene in λ phage encodes the λ repressor protein, which is crucial for maintaining the lysogenic state. This protein binds to specific operator sites on the phage DNA, repressing the expression of lytic genes and promoting lysogeny.
Analyze the effect of a mutation that inactivates cI: If the cI gene is inactivated, the λ repressor protein will not be produced. Without this repressor, the lytic genes will not be suppressed, and the phage will be unable to establish or maintain the lysogenic state.
Determine the life cycle outcome: In the absence of the λ repressor, the phage will default to the lytic cycle. This is because the lytic genes will be expressed unchecked, leading to the production of new phage particles and eventual lysis of the host cell.
Consider the broader implications: The inability to enter or maintain lysogeny means that the phage cannot integrate its genome into the host's genome, which is a hallmark of the lysogenic cycle. This could affect the phage's ability to persist in environments where host cells are scarce.
Summarize the mutation's impact: A mutation that inactivates the cI gene will prevent the phage from entering or maintaining the lysogenic cycle, forcing it to exclusively follow the lytic pathway.

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Lytic and Lysogenic Cycles

The lytic and lysogenic cycles are two distinct pathways that bacteriophages, like λ phage, can follow after infecting a bacterial host. In the lytic cycle, the phage replicates rapidly, leading to the destruction of the host cell and the release of new phage particles. In contrast, the lysogenic cycle involves the integration of the phage DNA into the host genome, allowing it to replicate along with the host cell without causing immediate harm.
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Decision Between Lytic and Lysogenic Cycles

cI Gene Function

The cI gene in λ phage encodes a repressor protein that is crucial for maintaining the lysogenic state. This protein binds to the operator region of the phage genome, inhibiting the expression of genes required for the lytic cycle. When cI is functional, it promotes lysogeny by preventing the activation of lytic genes, thus allowing the phage to coexist with the host.
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Functional Genomics

Mutations and Gene Inactivation

Mutations that inactivate the cI gene can disrupt the balance between the lytic and lysogenic cycles. If cI is nonfunctional, the repressor cannot inhibit lytic gene expression, leading to the activation of the lytic cycle. This results in the phage entering a lytic phase, causing cell lysis and the release of new phage particles, rather than integrating into the host genome and remaining dormant.
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X-Inactivation
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Domanda del libro di testo

Suppose that base substitution mutations sufficient to eliminate the function of the operator regions listed below were to occur. For each case, describe how transcription or life cycle would be affected.

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Domanda del libro di testo

Suppose that base substitution mutations sufficient to eliminate the function of the operator regions listed below were to occur. For each case, describe how transcription or life cycle would be affected.

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How would mutations that inactivate each of the following genes affect the determination of the lytic or lysogenic life cycle in mutated λ phage strains? Explain your answers.

int

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How would mutations that inactivate each of the following genes affect the determination of the lytic or lysogenic life cycle in mutated λ phage strains? Explain your answers.

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Domanda del libro di testo

How would mutations that inactivate each of the following genes affect the determination of the lytic or lysogenic life cycle in mutated λ phage strains? Explain your answers.

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Two different mutations affect PRE. Mutant 1 decreases transcription from the promoter to 10% of normal. Mutant 2 increases transcription from the promoter to 10 times greater than the wild type. How will each mutation affect the determination of the lytic or lysogenic life cycle in mutant λ phage strains? Explain your answers.

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