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Brookings Biology Kelly Riedell

POOL NOODLE OPERONS SP 1. The student can use representations and models to communicate scientific phenomena and solve academic problems. Brookings Biology Kelly Riedell. Pool Noodle Operons from: Kristen Dotti Catalyst Learning Curricula * Indicated slides borrowed from: Kim Foglia.

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Brookings Biology Kelly Riedell

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  1. POOL NOODLE OPERONSSP 1. The student can use representations and models to communicate scientific phenomena and solve academic problems. Brookings Biology Kelly Riedell Pool Noodle Operons from: Kristen Dotti Catalyst Learning Curricula* Indicated slides borrowed from: Kim Foglia Image from: http://www.eldontaylor.com/blog/wp-content/uploads/bigstock-On-Off-Switch-Shows-Energy-Sup-519917201-300x300.jpg

  2. Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. Enduring understanding 2.C: Organisms use feedback mechanisms to regulate growth and reproduction, and to maintain dynamic homeostasis. Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. a. Negative feedback mechanisms maintain dynamic homeostasis for a particular condition (variable) by regulating physiological processes, returning the changing condition back to its target setpoint. To foster student understanding of this concept, instructors can choose an illustrative example such as:  • Operons in gene regulation

  3. Essential knowledge 3.B.1: Gene regulation results in differential gene expression, leading to cell specialization. a. Both DNA regulatory sequences, regulatory genes, and small regulatory RNAs are involved in gene expression. Evidence of student learning is a demonstrated understanding of each of the following:  1. Regulatory sequences are stretches of DNA that interact with regulatory proteins to control transcription. To foster student understanding of this concept, instructors can choose an illustrative example such as:  • Promoters  • Terminators  • Enhancers 2. A regulatory gene is a sequence of DNA encoding a regulatory protein or RNA. b. Both positive and negative control mechanisms regulate gene expression in bacteria and viruses. Evidence of student learning is a demonstrated understanding of each of the following:  1. The expression of specific genes can be turned on by the presence of an inducer. 2. The expression of specific genes can be inhibited by the presence of a repressor. 3. Inducers and repressors are small molecules that interact with regulatory proteins and/or regulatory sequences. 4. Regulatory proteins inhibit gene expression by binding to DNA and blocking transcription (negative control). 5. Regulatory proteins stimulate gene expression by binding to DNA and stimulating transcription (positive control) or binding to repressors to inactivate repressor function. 6. Certain genes are continuously expressed; that is, they are always turned "on," e.g., the ribosomal genes.

  4. Essential knowledge 3.B.1: Gene regulation results in differential gene expression, leading to cell specialization. c. In eukaryotes, gene expression is complex and control involves regulatory genes, regulatory elements and transcription factors that act in concert. Evidence of student learning is a demonstrated understanding of each of the following:  1. Transcription factors bind to specific DNA sequences and/or other regulatory proteins.  2. Some of these transcription factors are activators (increase expression), while others are repressors (decrease expression). 3. The combination of transcription factors binding to the regulatory regions at any one time determines how much, if any, of the gene product will be produced. d. Gene regulation accounts for some of the phenotypic differences between organisms with similar genes. Learning Objectives: LO 3.18 The student is able to describe the connection between the regulation of gene expression and observed differences between different kinds of organisms. [See SP 7.1] LO 3.19 The student is able to describe the connection between the regulation of gene expression and observed differences between individuals in a population. [See SP 7.1] LO 3.20 The student is able to explain how the regulation of gene expression is essential for the processes and structures that support efficient cell function. [See SP 6.2] LO 3.21 The student can use representations to describe how gene regulation influences cell products and function. See SP 1.4]

  5. PROKARYOTES Genes with related functions grouped together = Operon • example: all enzymes in a metabolic pathway • If cell needs one, it needs them all! • Make ALL or NONE • Transcribed as ONE message (POLYCISTRONIC)

  6. Operons contain: STRUCTURAL GENES: code for proteins in metabolic pathway EX: trp A, B, C, D, E = enzymes for pathway that makes tryptophan REGULATORY GENES • promoter = RNA polymerase binding site • single promoter controls transcription of all genes in operon • transcribed as one unit & a single mRNA is made • operator = DNA binding site of repressor protein • some regulatory genes = code for regulatory proteins (EX: repressors, inducers)

  7. RNA polymerase RNA polymerase repressor promoter promoter enzyme1 1 enzyme2 2 enzyme3 3 enzyme4 4 operator operator When gene is turned ON: Polymerase binds promotermRNA is made (transcription)mRNA is turned into proteins by ribosomes DNA TATA mRNA gene1 gene2 gene3 gene4 gene1 gene2 gene3 gene4 gene1 gene2 gene3 gene4 TATA DNA When gene is turned OFF Repressor binds operatorRNA polymerase can’t transcribe gene Slide by Kim Foglia modified

  8. REPRESIBLE OPERONS Usually ON/repressor usually ACTIVECan be turned off (repressed)Genes for enzymes that make product always needed EX: trp operon makes enzymes used in essential amino acid synthesis • INDUCIBLE OPERONSUsually OFF/repressor INACTIVE Can be turned on (induced)Genes for enzymes that are only needed sometimes EX: lac operon makes enzymes used in lactose digestion

  9. Image from: http://1.bp.blogspot.com/-fiLbtgnhKj8/Uf_3riQiFfI/AAAAAAAAA7o/xK_DFm_P4OA/s1600/GeneDoping3_widec.jpg • ANABOLIC pathwaysChemical reactions that put together moleculesEX: trpoperon makes enzymes used to produce tryptophan • CATABOLIC pathwaysChemical reactions that break apart molecules EX: lac operon makes enzymes used in lactose digestion

  10. DIFFERENCE BETWEEN THE TWO IS WHAT MAKES REPRESSOR ACTIVE OR INACTIVE! REPRESSOR is usually INACTIVECells need to make tryptophan If tryptophan is available, don’t need to make it Tryptophan ACTIVATES repressorTURNS GENE OFF REPRESSOR is usually ACTIVECells don’t need to make lactose digesting enzymes if no lactose present If lactose is available, need to digest it Lactose INACTIVATES repressorTURNS GENE ON

  11. SLIDE FROM: Kim Foglia trp RNA polymerase repressor repressor repressor promoter repressor protein= INACTIVE operator tryptophan trp trp trp trp trp trp trp trp trp tryptophan – repressor protein Complex = ACTIVE VIDEO Repressibletrp operon: Codes for enzymes that synthesize tryptophan Synthesis pathway model When excess tryptophan is present, it binds to trp repressor protein & triggers repressor to bind to DNA • blocks (represses) transcription gene1 gene2 gene3 gene4 TATA DNA conformational change in repressor protein makes it ACTIVE! trp trp

  12. RNA polymerase repressor repressor repressor enzyme1 1 enzyme2 2 enzyme3 3 enzyme4 4 promoter repressor protein =ACTIVE operator lactose lac lac lac lac lac lac lac lactose – repressor protein Complex = INACTIVE SLIDE FROM: Kim Foglia VIDEO Induciblelac operon codes for enzymes for lactose digestion Digestive pathway model When lactose is present, binds to lac repressor protein & triggers repressor to release DNA • induces transcription lac gene1 gene2 gene3 gene4 TATA DNA mRNA lac conformational change in repressor protein makes it INACTIVE! lac

  13. NEGATIVE CONTROL Using REPRESSORS to TURN OFF genes = REPRESSIBLE and INDUCIBLE operons ARE BOTH TYPES OF NEGATIVE CONTROL ! ! ! ! http://3.bp.blogspot.com/-tArOpdcSKlQ/VDyOFD4hJ8I/AAAAAAAABw8/rEaxBPVNf-g/s1600/Electical%2BLight%2Bswitch...cartoon.jpeg

  14. POSITIVE CONTROL Using ENHANCER REGIONS and ACTIVATORS/INDUCERS to TURN ON genes = http://cdn.xl.thumbs.canstockphoto.com/canstock8046278.jpg

  15. POSTIVE CONTROL of Lactose operon What happens when concentration of glucose is LOW? LOW GLUCOSE → HIGH cAMP cAMP makes CAP active; starts transcription VIDEO GLUCOSE IS FOOD OF CHOICE CataboliteActivatorProtein Image from:http://image.slidesharecdn.com/18regulationofgeneexpression-130613012903-phpapp02/95/18-regulation-of-gene-expression-15-638.jpg?cb=1371087103

  16. POSTIVE CONTROL of Lactose operon What happens if BOTH GLUCOSE AND LACTOSE are present? GLUCOSE IS FOOD OF CHOICE Repressor is inactive but CAP activator is not activatedGene is unable to turn on at significant rate CataboliteActivatorProtein Image from:http://image.slidesharecdn.com/18regulationofgeneexpression-130613012903-phpapp02/95/18-regulation-of-gene-expression-15-638.jpg?cb=1371087103

  17. WHAT ABOUT EUKARYOTES • Genes for proteins that work together in a pathway are spread out on different chromosomes (NO OPERONS) • Separate control sequences for each gene • BOTH POSTIVE (enhancers) and NEGATIVE (repressors) control

  18. ACTIVATORS BIND TO ENHANCER region Image from: https://cellularphysiology.wikispaces.com/file/view/18_09ActivatorAction_3-L.jpg/465203668/18_09ActivatorAction_3-L.jpg

  19. MAKE A CONNECTION WHERE DO ACTIVATOR proteins come from? Images fromhttp://images.slideplayer.com/1/273672/slides/slide_49.jpg http://image.slidesharecdn.com/45lecturepresentation-101204060035-phpapp01/95/chapter-45-textbook-presentation-33-728.jpg?cb=1291442560

  20. ACTIVATED ENHANCERS attach to TRANSCRIPTION FACTORS and FOLD DNAback onto itself VIDEO Image from: https://cellularphysiology.wikispaces.com/file/view/18_09ActivatorAction_3-L.jpg/465203668/18_09ActivatorAction_3-L.jpg

  21. RNA POLYMERASE attaches to TRANSCRIPTION INTIATION COMPLEX to start transcription (GENE is turned ON!) Image from: https://cellularphysiology.wikispaces.com/file/view/18_09ActivatorAction_3-L.jpg/465203668/18_09ActivatorAction_3-L.jpg

  22. Different genes have different enhancer regionsand are controlled by differentactivators Image from: http://image.slidesharecdn.com/18regulationofgeneexpression-130613012903-phpapp02/95/18-regulation-of-gene-expression-35-638.jpg?cb=1371087103

  23. DIFFERENT ENHANCER sequences canTURN ON a gene in DIFFERENT KINDS of cells at DIFFERENT TIMES. Image from: https://cellularphysiology.wikispaces.com/file/view/18_09ActivatorAction_3-L.jpg/465203668/18_09ActivatorAction_3-L.jpg

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