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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2:59 minutes

Problem 9

Textbook Question

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

Verified step by step guidance

Understand the context: The GAL genes in yeast and the lac genes in bacteria are both involved in the metabolism of specific sugars (galactose and lactose, respectively). However, their transcriptional regulation mechanisms differ due to the differences between eukaryotic and prokaryotic systems.

Step 1: Describe the regulation of GAL genes in yeast. In yeast, the GAL genes are regulated by a system involving activators (e.g., Gal4), repressors (e.g., Gal80), and inducers (e.g., galactose). When galactose is present, it binds to Gal3, which interacts with Gal80 to release its inhibition on Gal4. Gal4 then binds to upstream activating sequences (UAS) to promote transcription.

Step 2: Describe the regulation of lac genes in bacteria. In bacteria, the lac operon is regulated by the LacI repressor and the CAP-cAMP complex. When lactose is absent, the LacI repressor binds to the operator region, preventing transcription. When lactose is present, it is converted to allolactose, which binds to LacI, causing it to release the operator. Additionally, the CAP-cAMP complex enhances transcription when glucose levels are low.

Step 3: Compare the two systems. Both systems use regulatory proteins to control gene expression in response to the presence of specific sugars. However, the GAL system in yeast relies on activators and a more complex interplay of proteins, while the lac operon in bacteria primarily uses a repressor and an activator.

Step 4: Contrast the two systems. The GAL system operates in a eukaryotic context, involving chromatin remodeling and transcription factors, while the lac operon operates in a prokaryotic context, where transcription and translation are coupled. Additionally, the GAL system has a more modular and flexible regulatory mechanism compared to the simpler lac operon.

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Key Concepts

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

Transcriptional Regulation

Transcriptional regulation refers to the mechanisms that control the transcription of genes, determining when and how much of a gene product is produced. In both yeast and bacteria, this regulation is crucial for responding to environmental changes and metabolic needs. It involves various proteins, such as transcription factors, that bind to specific DNA sequences to enhance or inhibit gene expression.

GAL Genes in Yeast

The GAL genes in yeast are involved in the metabolism of galactose and are regulated by a complex system that includes the GAL4 protein, which acts as an activator. When galactose is present, GAL4 binds to the UAS (upstream activating sequence) of the GAL genes, promoting their transcription. This regulation is an example of eukaryotic gene control, which often involves chromatin remodeling and multiple regulatory elements.

Lac Operon in Bacteria

The lac operon in bacteria, particularly E. coli, is a classic model of gene regulation that controls the metabolism of lactose. It consists of structural genes (lacZ, lacY, lacA) and is regulated by the lac repressor and CAP (catabolite activator protein). In the absence of lactose, the repressor binds to the operator, blocking transcription, while the presence of lactose and glucose levels influence the operon's activity, showcasing prokaryotic regulation mechanisms.

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Related Practice

Multiple Choice

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

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Multiple Choice

Which of the following is the purpose of the GAL gene system?

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.

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.

473

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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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