Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

13. Gene Regulation in Eukaryotes

GAL Regulation

Genetics

13. Gene Regulation in Eukaryotes

GAL Regulation

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2:31 minutes

Problem 22b

Textbook Question

Explain how the following mutations would affect transcription of the yeast GAL1 gene in the presence of galactose.
A deletion of the entire GAL3 gene.

Verified step by step guidance

Understand the role of the GAL3 gene in the regulation of the GAL1 gene. GAL3 encodes a protein that acts as a sensor and inducer in the presence of galactose, facilitating transcription activation of GAL1.

Recognize that in the presence of galactose, the GAL3 protein binds galactose and interacts with the GAL80 repressor, relieving its inhibition on the GAL4 activator, which then promotes transcription of GAL1.

Consider the effect of deleting the entire GAL3 gene: without GAL3 protein, the signal from galactose cannot be properly transmitted to relieve GAL80 repression.

Predict that because GAL80 remains bound to GAL4, the transcriptional activation of GAL1 will be impaired or significantly reduced despite the presence of galactose.

Conclude that the deletion of GAL3 leads to a failure in induction of GAL1 transcription in response to galactose, resulting in low or no expression of the GAL1 gene under inducing conditions.

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Key Concepts

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

Role of GAL3 in Galactose Signaling

GAL3 encodes a sensor protein that binds galactose and ATP, triggering a signal that relieves repression of GAL gene transcription. Without GAL3, the cell cannot effectively detect galactose, preventing activation of GAL1 transcription despite galactose presence.

Regulation of GAL1 Gene Transcription

The GAL1 gene is regulated by a network of proteins including GAL4 (activator), GAL80 (repressor), and GAL3 (inducer). In the presence of galactose, GAL3 binds GAL80, freeing GAL4 to activate GAL1 transcription. Disruption in this pathway affects GAL1 expression.

Impact of Gene Deletion on Regulatory Pathways

Deleting the GAL3 gene removes a critical component of the galactose induction pathway, leading to failure in signal transduction. This results in continued repression of GAL1 transcription, demonstrating how gene deletions can disrupt regulatory networks and gene expression.

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Related Practice

Textbook Question

Explain how the following mutations would affect transcription of the yeast GAL1 gene in the presence of galactose.

A deletion of one of the four UAS_G elements upstream from the GAL1 gene.

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Textbook Question

Explain how the following mutations would affect transcription of the yeast GAL1 gene in the presence of galactose.

A mutation within the GAL80 gene that blocks the ability of Gal80 protein to interact with Gal3p.

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Textbook Question

Explain how the following mutations would affect transcription of the yeast GAL1 gene in the presence of galactose.

A point mutation in the GAL1 core promoter that alters the sequence of the TATA box.

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Textbook Question

Explain how the following mutations would affect transcription of the yeast GAL1 gene in the presence of galactose.

A deletion within the GAL4 gene that removes the region encoding amino acids 1 to 100.

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Textbook Question

Regulation of the lac operon in E. coli and regulation of the GAL system in yeast are analogous in that they both serve to adapt cells to growth on different carbon sources. However, the transcriptional changes are accomplished very differently. Consider the conceptual similarities and differences as you address the following.

Compare and contrast how these two systems are negatively regulated such that they are downregulated in the presence of glucose.

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Textbook Question

Compare and contrast the cis-regulatory elements of the lac operon and GAL gene system.

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Textbook Question

Regulation of the lac operon in E. coli and regulation of the GAL system in yeast are analogous in that they both serve to adapt cells to growth on different carbon sources. However, the transcriptional changes are accomplished very differently. Consider the conceptual similarities and differences as you address the following.

Compare and contrast the roles of the lac operon inducer in bacteria and Gal3p in eukaryotes in the regulation of their respective systems.

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Multiple Choice

Which of the following statements is accurate regarding the regulation of gal genes in yeast?

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