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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Problem 22e

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.

Verified step by step guidance

Understand the role of the TATA box in transcription: The TATA box is a core promoter element that helps position RNA polymerase II and general transcription factors to initiate transcription at the correct site.

Recognize that a point mutation in the TATA box sequence can disrupt the binding affinity of the transcription machinery, potentially reducing or abolishing the recruitment of RNA polymerase II.

Consider that in the presence of galactose, the GAL1 gene is normally activated by specific transcription factors, but if the core promoter is defective, these activators cannot effectively initiate transcription.

Predict that the mutation would likely lead to decreased or no transcription of the GAL1 gene despite the presence of galactose, because the basal transcriptional machinery cannot properly assemble at the promoter.

Summarize that the mutation in the TATA box impairs the fundamental step of transcription initiation, overriding the positive regulatory signals from galactose-induced activators.

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Key Concepts

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

Role of the TATA Box in Transcription Initiation

The TATA box is a core promoter element that helps position RNA polymerase II for accurate transcription initiation. It is recognized by the TATA-binding protein (TBP), which is part of the transcription factor complex. Mutations in the TATA box can disrupt TBP binding, leading to reduced or abolished transcription initiation.

GAL1 Gene Regulation in Yeast

The GAL1 gene in yeast is induced in the presence of galactose and repressed when glucose is available. Its expression depends on the activation of transcription factors that bind upstream regulatory sequences, but proper transcription also requires an intact core promoter, including the TATA box, to recruit the transcription machinery.

Effects of Point Mutations on Promoter Function

A point mutation in the promoter region can alter critical DNA sequences necessary for transcription factor binding. In the TATA box, even a single nucleotide change can impair the assembly of the pre-initiation complex, reducing transcription efficiency or completely preventing gene expression despite the presence of activating signals like galactose.

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Related Practice

Textbook Question

Compare and contrast the transcriptional regulation of GAL genes in yeast with that of the lac genes in bacteria.

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Textbook Question

A modification of the two-hybrid system, called the one-hybrid system, is used for identifying proteins that can bind specific DNA sequences. In this method, the DNA sequence to be tested, the bait, is fused to a TATA box to drive expression of a reporter gene. The reporter gene is often chosen to complement a mutant phenotype; for example, a HIS gene may be used in a his⁻ mutant yeast strain. A cDNA library is constructed with the cDNA sequences translationally fused to the GAL4 activation domain and transformed into this yeast strain. Diagram how trans-acting proteins that bind to cis-acting regulatory sequences can be identified using a one-hybrid screen.

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

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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 of the entire GAL3 gene.

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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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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.

Key Concepts

Role of the TATA Box in Transcription Initiation

GAL1 Gene Regulation in Yeast

Effects of Point Mutations on Promoter Function

Watch next

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.