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What evidence established that lactose serves as the inducer of a gene whose product is related to lactose metabolism?
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Ch. 15 - Regulation of Gene Expression in Bacteria
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
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TOC.tableOfContents
- Ch. 1 - Introduction to Genetics16
- Ch. 2 - Mitosis and Meiosis28
- Ch. 3 - Mendelian Genetics37
- Ch. 4 - Modification of Mendelian Ratios53
- Ch. 5 - Sex Determination and Sex Chromosomes32
- Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement37
- Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes36
- Ch. 8 - Genetic Analysis and Mapping in Bacteria and Bacteriophages24
- Ch. 9 - DNA Structure and Analysis38
- Ch. 10 - DNA Replication29
- Ch. 11 - Chromosome Structure and DNA Sequence Organization22
- Ch. 12 - The Genetic Code and Transcription36
- Ch. 13 - Translation and Proteins27
- Ch. 14 - Gene Mutation, DNA Repair, and Transposition34
- Ch. 15 - Regulation of Gene Expression in Bacteria22
- Ch. 16 - Regulation of Gene Expression in Eukaryotes37
- Ch. 17 - Recombinant DNA Technology27
- Ch. 18 - Genomics, Bioinformatics, and Proteomics30
- Ch. 19 - The Genetics of Cancer21
- Ch. 20 - Quantitative Genetics and Multifactorial Traits37
- Ch. 21 - Population and Evolutionary Genetics45
Klug10th EditionEssentials of GeneticsISBN: 9780135588789Non è quello che usi tu?Cambia libro di testo
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Klug 10th EditionCh. 15 - Regulation of Gene Expression in BacteriaProblema 1e
Klug 10th EditionCh. 15 - Regulation of Gene Expression in BacteriaProblema 1eCapitolo 15, Problema 1e
How do we know that the trp operon is a repressible control system, in contrast to the lac operon, which is an inducible control system?
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Understand the basic definitions: A repressible operon is typically 'on' and actively transcribing until it is turned 'off' by a specific molecule (corepressor), whereas an inducible operon is usually 'off' and requires an inducer molecule to turn it 'on'.
Examine the trp operon: It controls the synthesis of tryptophan. When tryptophan levels are low, the operon is active, allowing the production of enzymes needed to make tryptophan. When tryptophan is abundant, it acts as a corepressor by binding to the repressor protein, enabling the repressor to bind the operator and block transcription.
Analyze the lac operon: It controls the breakdown of lactose. In the absence of lactose, the repressor binds the operator and prevents transcription. When lactose is present, it acts as an inducer by binding to the repressor, causing it to release from the operator and allowing transcription to proceed.
Compare the mechanisms: The trp operon is repressible because it is normally active and turned off by the presence of a corepressor (tryptophan), while the lac operon is inducible because it is normally inactive and turned on by the presence of an inducer (lactose).
Summarize the key difference: The trp operon responds to the end product (tryptophan) to repress gene expression, whereas the lac operon responds to the substrate (lactose) to induce gene expression.
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Repressible Operon
A repressible operon is typically active but can be turned off when a specific molecule, often the end product of a pathway, binds to a repressor protein. This binding enables the repressor to attach to the operator region, blocking transcription. The trp operon is repressible because it is usually on and is turned off when tryptophan is abundant.
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03:45
Arabinose Operon
Inducible Operon
An inducible operon is usually off and requires the presence of a specific inducer molecule to activate transcription. The inducer inactivates the repressor, allowing gene expression. The lac operon is inducible because it is off until lactose is present, which induces the operon to produce enzymes for lactose metabolism.
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Percorso guidato
04:29Induced Mutations
Mechanism of Gene Regulation in Operons
Operons regulate gene expression through interactions between repressors, inducers/corepressors, and operator DNA sequences. Understanding how these molecules influence RNA polymerase binding and transcription initiation is key to distinguishing repressible and inducible systems, as seen in the contrasting control of the trp and lac operons.
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06:55Lac Operon Regulation
Pratica correlata
Domanda del libro di testo
Contrast positive versus negative control of gene expression.
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Domanda del libro di testo
Contrast the role of the repressor in an inducible system and in a repressible system.
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Domanda del libro di testo
How do we know that the lac repressor is a protein?
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Domanda del libro di testo
What led researchers to conclude that a repressor molecule regulates the lac operon?
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Domanda del libro di testo
Write a brief essay that discusses why you think regulatory systems evolved in bacteria (i.e., what advantages do regulatory systems provide to these organisms?), and, in the context of regulation, discuss why genes related to common functions are found together in operons.
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