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BIO311: Molecular Biology

Unit 7: Regulation of Gene Expression   The synthesis of a complementary RNA strand from a DNA template takes place in somewhat different ways in prokaryotes and in eukaryotes, as you learned in Unit 5.  In this unit you will study gene expression in more detail.  Synchronized gene expression on prokaryotes is directed in operons, wherein certain genes that are next to each other are regulated by the binding or not binding of a repressor to an upstream region.  In the case of eukaryotes, transcription is synchronizing expression of genes that are scattered throughout the chromosome(s).  In eukaryotes, genes are expressed only if a set of enhancers are present and a complex transcription initiation complex can form.  This can lead to tissue- and activity-specific gene expression, when distant genes express the same set of enhancers.  Epigenetics means "in addition to" genetics, and it is studying why genes with identical sequences are expressed differently.  Epigenetic changes are chemical modifications (not sequence changes) that living organisms pick up during their life as a response to environmental stimuli, e.g., nutrition.  The result is turning genes off and on, through making the chromosomal structure more or less compact.  The more compact structure interferes with gene transcription.

Unit 7 Time Advisory
This unit should take you approximately 9.5 hours to complete.

☐    Subunit 7.1: 5.0 hours

☐    Subunit 7.2: 2.5 hours

☐    Subunit 7.3: 2.0 hours

Unit7 Learning Outcomes
Upon successful completion of this unit, students will be able to: - Compare and contrast prokaryotic and eukaryotic gene expression. - Discuss, compare, and contrast inducible and repressible operons in bacteria. - Describe diverse regulatory elements in eukaryotic transcription. - Predict activation and repression of operons. - Predict tissue specific gene expression based on the availability of enhancers. - Describe how epigenetic modifications regulate gene expression for generations. - Describe how epigenetic modifications change gene expression without changing the genome.

7.1 Prokaryotic Gene Expression   7.1.1 Overview   - Reading: NCBI Bookself: Cooper's "Transcription in Prokaryotes" Link: NCBI Bookself: Cooper's "Transcription in Prokaryotes" (HTML)
 
Instruction: Please study the "RNA Polymerase and Transcription" section on this page.  Please note that in prokaryotes, the genes that should be expressed at the same time are often located next to each other.
 
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7.1.2 Inducible Operon: Lac Operon   - Reading: NCBI Bookself: Cooper's "Transcription in Prokaryotes" Link: NCBI Bookself: Cooper's "Transcription in Prokaryotes" (HTML)
 
Instruction:  Please study the "Repressors and Negative Control of Transcription" and "Positive Control of Transcription" sections on this page.  Please note that the repressor inhibits transcription unless it is inactivated by the inducer.  The inducer is allolactose for Lac operon. Inducible operons are common in the regulation of catabolic pathways.
 
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  • Assessment: University of Arizona: The Biology Project: "Molecular Genetics of Prokaryotes" Link:  University of Arizona: The Biology Project: "Molecular Genetics of Prokaryotes" (HTML)
     
    Instruction: Please complete this problem set.  There are 14 problems in the set, and each problem is linked to a brief tutorial page.  After answering a question, please click on and study each tutorial page as well.
     
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7.1.3 Repressible Operon: Trp Operon   - Reading: NCBI Bookself: Cooper's "Transcription in Prokaryotes" Link: NCBI Bookself: Cooper's "Transcription in Prokaryotes" (HTML)
 
Instruction:  Please study the "Transcriptional Attenuation" section on this page.  Please note that the repressor cannot interfere with transcription unless it is activated by the co-repressor. The co-repressor is tryptophan for Trp operon.  Repressible operons are common in the regulation of anabolic pathways.
 
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7.2 Eukaryotic Gene Expression   7.2.1 Overview   - Reading: NCBI Bookself: Lodish et al.'s "Eukaryotic Gene Control: Purposes and General Principles" Link: NCBI Bookself: Lodish et al.'s "Eukaryotic Gene Control: Purposes and General Principles" (HTML)
 
Instruction: Please study the introduction and "Most Genes in Higher Eukaryotes Are Regulated by Controlling Their Transcription" sections on this page.  Please note that while their genomic DNAs are identical, different cell types are expressing different proteins in eukaryotes.
 
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7.2.2 Regulatory Elements   - Reading: NCBI Bookself: Lodish et al.'s "Eukaryotic Gene Control: Purposes and General Principles" Link: NCBI Bookself: Lodish et al.'s "Eukaryotic Gene Control: Purposes and General Principles" (HTML)
 
Instruction: Please study the "Regulatory Elements in Eukaryotic DNA Often Are Many Kilobases from Start Sites" section on this page.  Please note that in eukaryotes, the genes that should be expressed at the same time are often far from each other on the chromosome.
 
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  • Assessment: University of Arizona: The Biology Project: "Eukaryotic Gene Expression Problem Set" Link:  University of Arizona: The Biology Project: "Eukaryotic Gene Expression Problem Set" (HTML)
     
    Instruction: Please complete this problem set.  There are 13 problems in the set, and each problem is linked to a brief tutorial page.  After answering a question, please click on and study each tutorial page as well.

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7.3 Epigenetics and Gene Silencing   - Reading: Scitable: Dr. Laura Bonetta’s “Epigenomics: The New Tool in Studying Complex Diseases" Link:  Scitable: Dr. Laura Bonetta’s “Epigenomics: The New Tool in Studying Complex Diseases" (HTML)
 
Instruction: Please study this page.  Epigenetics refers to anything that changes gene expression without changing the DNA sequence of the genome.  These changes are chemical modifications, e.g., DNA methylation and histone acethylation.  Epigenetic changes turn genes on and off in the genome.
 
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  • Reading: Scitable: Sarah Nelson’s “Comparative Methylation Hybridization" Link:  Scitable: Sarah Nelson’s “Comparative Methylation Hybridization" (HTML)
     
    Instruction: Please study this page.  Please note that epigenetic changes respond quickly to environmental stimuli, e.g., famine and substances in our food.  Research shows that epigenetic changes can be inherited.
     
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