General Biology BIOL 1005
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This 3 page Class Notes was uploaded by Megan Wiggs on Tuesday October 11, 2016. The Class Notes belongs to BIOL 1005 at Virginia Polytechnic Institute and State University taught by MV lipscomb in Fall 2016. Since its upload, it has received 3 views. For similar materials see General Biology in Science at Virginia Polytechnic Institute and State University.
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Date Created: 10/11/16
Control of Gene Expression Lesson 13 All body cells have the same genes - Different body cells use different genes Gene Expression Changes Over Time Prokaryotes regulate gene expression in response to environmental changes Eukaryotes regulate gene expression for development and to maintain homeostasis Transcriptional Regulation is the Most Common Type Transcriptional regulation is particularly common in prokaryotes A promoter region is where the RNA polymerase attaches - Regulatory proteins may affect the ability for RNA polymerase to attach - True to both Eukaryotes and prokaryotes A promoter region consists of regulatory DNA sequence upstream from transcription start site RNA polymerase binds to the core promoter to initiate transcription. Regulatory proteins may affect the ability of RNA polymerase to bind to the promoter Many Prokaryotic Genes are Organized into Operons Genes in operon have related functions DNA components of Operon Regulation: Core Promoter Region Operator- only associated with repressor proteins Activator Binding Sit- May be close to the core promoter or further away Operons always have a promoter, but may have any number/combination of activator binding sites and operators The lac operon produces the proteins required for lactose metabolism - Both positively and negatively controlled - Inhibits transcription when lactose is absent - CAP activator protein promotes transcription when glucose is absent Presence of glucose= activator Presence of lactose= repressor Regulation occurs at all stages in eukaryotes Transcriptional regulation: - Transcription factors (regulatory proteins) - Chromatin Structure-Epigenetic regulation Post Transcriptional Regulation: - mRNA alternative splicing - mRNA transport - Inhibition of translation Post translational regulation - Protein activity - Protein stability Transcriptional regulation in Eukaryotes Regulatory proteins/transcription factors - Some require activation Epigenetic - Changes in chromosome without change DNA sequence o Chromatin structure- packaging level or chemical modifications o Chromosome inactivation Barr body-inactive X chromosome Post-transcriptional regulation in Eukaryotes Alternative splicing - 2 or more genes from the same primary mRNA transcript - takes place in the cytoplasm Inhibition of transport inhibition of translation - Reduced availability of molecules needed for translation - Molecules block translation of mRNA Post translational regulation in Eukaryotes Protein Activity - Addition or removal of phosphate groups Protein stability - Proteins are degraded (regulated gene expression in the cell) Human gene expression: Summary slide • 1. Each human cell contains the same set of genes ( approx. 21,000.) • 2. Human body à about 200 different cell types • 3. A fraction of the genes are expressed in each cell. • 4. Differential gene expression results in specialized cells. • 5. Differential gene expression occurs over time during development. • 6. Differential gene expression occurs to maintain homeostasis.
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