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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1:21 minutes

Problem 22d

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.

Verified step by step guidance

Understand that the GAL1 gene in yeast is regulated by upstream activating sequences (UASG), which are binding sites for transcriptional activators that enhance transcription in the presence of galactose.

Recognize that the presence of multiple UASG elements (four in this case) allows for a stronger or more robust transcriptional activation due to cooperative binding of activators.

Consider that a deletion of one UASG element reduces the number of binding sites available for activators, potentially decreasing the overall transcriptional activation of the GAL1 gene.

Analyze how this reduction might affect the transcription rate: fewer activator binding sites can lead to lower recruitment of the transcriptional machinery, thus reducing mRNA synthesis from the GAL1 gene when galactose is present.

Conclude that while transcription will still occur in the presence of galactose (since other UASG elements remain), the efficiency or level of transcription is expected to be diminished compared to the wild-type gene with all four UASG elements intact.

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Key Concepts

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

Upstream Activating Sequences (UAS)

UAS elements are specific DNA sequences located upstream of a gene that serve as binding sites for transcriptional activators. In yeast, UASG elements enhance transcription of the GAL1 gene by recruiting activator proteins in response to galactose, increasing RNA polymerase II recruitment and gene expression.

Transcriptional Regulation of the GAL1 Gene

The GAL1 gene is regulated by the presence of galactose, which activates transcription through binding of regulatory proteins to UASG sites. This regulation ensures GAL1 is expressed only when galactose is available, enabling yeast to metabolize this sugar efficiently.

Effects of Deletions in Regulatory DNA Elements

Deleting one of the UASG elements reduces the number of activator binding sites, potentially decreasing transcriptional activation. This can lead to lower GAL1 expression levels in the presence of galactose, as fewer activators can bind and stimulate transcription.

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Related Practice

Multiple Choice

The GAL gene system is activated in which of the following conditions?

When the GAL gene system is activated, galactose binds to the UAS regulatory region.

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 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

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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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 UASG elements upstream from the GAL1 gene.

Key Concepts

Upstream Activating Sequences (UAS)

Transcriptional Regulation of the GAL1 Gene

Effects of Deletions in Regulatory DNA Elements

Watch next

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.