Chapter 17_post

Genetics: A Conceptual Approach

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Unformatted text preview: Chapter 17 Control of Gene Expression in Eukaryotes Dr. Ed Otto George Mason University Key objectives Discuss some of the circumstances associated with variation in gene expression Review different mechanisms that can control gene expression in eukaryotes Gene Expression All cells in an organism contain the same genetic information Not all gene products are needed at all times in all cells, thus gene expression is a highly regulated process Gene Expression Changes in gene expression occur: 1. during development- cells become committed to developing specific cell types- this process, called cell determination, is accompanied by changes in gene expression undifferentiated precursor cell skin cell muscle cell Gene x- not expressed Gene y- expressed Gene z- expressed Gene x- expressed Gene y- not expressed Gene z- expressed Some genes are expressed in only one cell type; other genes are expressed in both cell types Gene Expression Changes in gene expression occur: 2. in response to alterations in environmental or physiological conditions- gene expression may increase or decrease in response to external or internal stimuli Environmental Temperature Blood Glucose Levels Low High Low High Gene a- expressed (high) Gene b- not expressed Gene a- expressed (low) Gene b- expressed Gene d- not expressed Gene expression induced by higher temp. Gene expression inhibited by higher temp. Gene d- expressed Gene Expression Changes in gene expression occur: 3. during pathogenesis - gene expression may be altered in disease states Normal Cell Cancer Cell Uninfected Cell Infected Cell Viral genes : Not present Cellular genes : Gene f- not expressed Gene h- expressed Gene i- not expressed Gene j- expressed Gene i- expressed Gene j- not expressed Viral genes : Gene v1- expressed Cellular genes : Gene f- expressed Gene g- not expressed e.g. oncogene e.g. tumor suppressor gene Monitoring Gene Expression Gene expression can be evaluated using a variety of methods One approach is the use of DNA microarrays- DNA microarrays are used to simultaneously monitor the expression of thousands of genes- Microarrays consist of known gene sequences attached to a solid support, which are hybridized to mRNAs isolated from cells of interest- This approach can be used to identify genes that are expressed differently in different cell types Control of Gene Expression Genes are DNA sequences that are transcribed into RNA Structural genes- encode proteins used in metabolism or as structural elements (e.g. gene encoding a glycolytic enzyme) Regulatory genes- encode products (RNA or proteins) that interact with other sequences and affect the transcription or translation of those sequences (e.g. gene encoding a transcription activator protein) Regulating Gene Expression...
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This note was uploaded on 05/06/2010 for the course BIO 311 taught by Professor Otto during the Spring '10 term at George Mason.

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Chapter 17_post - Chapter 17 Control of Gene Expression in...

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