CH 8 Control of gene expression

CH 8 Control of gene expression - 11/2/09 Chapter 8 Control...

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11/2/09 1 Chapter 8 Control of gene expression Cells from the same organism can be so…different! How does this happen?
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11/2/09 2 08_02_genetic.instruction.part1 Different cell types contain the same DNA Cell differentiation must be due to changes in gene expression
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11/2/09 3 First cat was cloned at A&M named “cc” Epigenetic effects may prevent efficient cloning of most mammals from somatic cells. Gene expression can be regulated at many steps But transcriptional control is paramount Early stage regulation – very economical, but takes time Late stage regulation – very fast, but not necessarily economical.
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11/2/09 4 Control of transcription initiation Binding of regulatory proteins to regulatory DNA sequences acts as a switch to control transcription initiation (binding of RNA polymerase to a promoter) Regulatory DNA sequences: May be as small as 10 base pairs May be longer than 10,000 base pairs (eukaryotes) Usually located upstream of initiation site Gene regulatory proteins: Bind to regulatory DNA sequences (sequence-specific) Positive acting - activators Negative acting - repressors Uniform diameter Regulatory DNA sequences present sequence-specific surface features on the DNA helix Gene regulatory proteins recognize these features at the major groove and form various types of contacts (H-bonds, ionic bonds, hydrophobic interactions) usually without disrupting the base pairing H-bonds.
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11/2/09 5 Regulatory proteins typically form ~20
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CH 8 Control of gene expression - 11/2/09 Chapter 8 Control...

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