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Principles of Biology – Bio 101
Fall Quarter
Lake Tahoe Community College
Instructor: Sue Kloss
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Chapter 18 – Gene Regulation
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I.
Gene Regulation in Prokaryotes
A. Proteins interacting with DNA turn prokaryotic genes on or off in response to environmental changes
1. Operons
2. genotype to phenotype – is called gene expression
3. A gene that is turned on is being translated into specific protein molecules
4. Control of gene expression makes it possible for cells to produce specific kinds of proteins when and where
they are needed
5. Operons in e. coli, which changes its activities from time to time in response to its environment
6. The trp operon = repressible operon – turns off gene
a. Repressor and corepressor
7. Lac operon- genes produce enzymes to deal with lactose – inducible operon – turns on gene
b. inducer
8. regulatory gene
9.
A third type of operon uses activators, which are proteins that turn operons ON by binding to DNA. These
proteins make it easier for RNA polymerase to bind to the promoter, rather than by blocking RNA
polymerase. – positive gene regulation
B. Prokaryotes and eukaryotes must alter gene expression depending on internal or external environment, and in
addition, eukaryotes must develop and maintain multiple cell types. Each cell type, in each stage of life, has the
same genome, but expresses a different set of genes.
II. Cellular Differentiation and cloning of Eukaryotes
A. Differentiation yields a variety of cell types, each expressing a different combination of genes
1. Differentiation
2. Control points for regulation of genes in eukaryotic cells
a. Regulation of chromatin
1. Histone modification\
2. DNA methylation
3. Epigenetic inheritance
b. Regulation of transcription initiation
1. Organization of typical eukaryotic gene
2. Roles of transcription factors and transcription initiation complex
3. Control elements
4. Coordinately controlled genes
c. Post transcriptional regulation
1. RNA processing and degradation
2. Initiation of translation
3. Protein processing, activation and degradation
B. Differential gene expression: DNA is in each cell – the entire library.
Lesson Objectives Ch. 18
1. Explain the adaptive advantage of genes grouped into an operon.
2. Using the trp operon as an example, draw and label, and then explain the concept of an operon and the function of the
operator, repressor, and corepressor.
3. Distinguish between structural and regulatory genes.
4. Describe how the lac operon functions and provide details on the role of the inducer, allolactose.
5. Explain how repressible and inducible enzymes differ and how those differences reflect differences in the pathways they
control.
6. Distinguish between positive and negative control of gene expression.
7. Compare the structure and organization of prokaryotic and eukaryotic genomes.
10. Distinguish between heterochromatin and euchromatin.
11. Explain the relationship between differentiation and differential gene expression.
12. Describe the most important point in the “pipeline of regulation” that gene expression is generally controlled.
13. Explain how DNA methylation and histone acetylation affect chromatin structure and the regulation of transcription.
14. Define epigenetic inheritance.
15. Describe the processing of pre-mRNA in eukaryotes.
16. Define control elements and explain how they influence transcription.
17. Explain the role that promoters, enhancers, activators, and repressors may play in transcriptional control.
18. Describe the process and significance of alternative RNA splicing.
19. Describe factors that influence the life span of mRNA in the cytoplasm. Compare the longevity of mRNA in prokaryotes
and in eukaryotes.
20. Explain how gene expression may be controlled at the translational and post-translational level.
21. Draw, label, and describe briefly the previous 8 or 9 different processes (the “pipeline”, as pictured in the book) for
regulating eukaryotic genes.