POOL NOODLE OPERONS Slide show by Kelly RiedellBrookings

POOL NOODLE OPERONS Slide show by Kelly Riedell/Brookings Biology Pool Noodle Operons from: Kristen Dotti Catalyst Learning Curricula * Indicated slides borrowed from: Kim Foglia Images by Kelly Riedell/Brookings Biology

TOPIC 6. 5 Regulation of Gene Expression LEARNING OBJECTIVE IST-2. A Describe the types of interactions that regulate gene expression. IST-2. A. 1 Regulatory sequences are stretches of DNA that interact with regulatory proteins to control transcription. IST-2. B. 1 Both prokaryotes and eukaryotes have groups of genes that are coordinately regulated— a. In prokaryotes, groups of genes called operons are transcribed in a single m. RNA molecule. The lac operon is an example of an inducible system. b. In eukaryotes, groups of genes may be influenced by the same transcription factors to coordinately regulate expression. LEARNING OBJECTIVE IST-2. C Explain how the binding of transcription factors to promoter regions affects gene expression and/or the phenotype of the organism. ESSENTIAL KNOWLEDGE IST-2. C. 1 Promoters are DNA sequences upstream of the transcription start site where RNA polymerase and transcription factors bind to initiate transcription. IST-2. C. 2 Negative regulatory molecules inhibit gene expression by binding to DNA and blocking transcription. IST-2. D. 1 Gene regulation results in differential gene expression and influences cell products and function. IST-2. D. 2 Certain small RNA molecules have roles in regulating gene expression. CED page 111 Think-Pair-Share Students build a model of transcription using pool noodles that can be purchased at a dollar store. Using everyday materials, such as tape, colored paper, yarn (or string), and markers, they identify the promoter region, TATA box, transcription start site, and terminal sequence. They describe the process of transcription from the initial binding of the transcription factors to the production of the transcript. This can be introduced or de-briefed using a Think-Pair-Share approach.

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)

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 m. RNA is made – operator = DNA binding site of repressor protein – some regulatory genes = code for regulatory proteins (EX: repressors, inducers)

When gene is turned ON: Polymerase binds promoter m. RNA is made (transcription) m. RNA is turned into proteins by ribosomes DNA RNA TATA polymerase 1 promoter operator 2 3 4 enzyme 1 gene 1 enzyme 2 gene 2 enzyme 3 gene 3 enzyme 4 gene 1 gene 2 gene 3 gene 4 m. RNA polymerase TATA promoter repressor operator Slide by Kim Foglia modified DNA When gene is turned OFF Repressor binds operator RNA polymerase can’t transcribe gene

• REPRESIBLE OPERONS Usually ON/repressor usually ACTIVE Can be turned off (repressed) Genes for enzymes that make product always needed EX: trp operon makes enzymes used in essential amino acid synthesis • INDUCIBLE OPERONS Usually 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

Image from: http: //1. bp. blogspot. com/-fi. Lbtgnh. Kj 8/Uf_3 ri. Qi. Ff. I/AAAAA 7 o/x. K_DFm_P 4 OA/s 1600/Gene. Doping 3_widec. jpg • ANABOLIC pathways Chemical reactions that put together molecules EX: trp operon makes enzymes used to produce tryptophan • CATABOLIC pathways Chemical reactions that break apart molecules EX: lac operon makes enzymes used in lactose digestion

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

SLIDE FROM: Kim Foglia Repressible trp operon: VIDEO 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 RNA polymerase trp repressor TATA gene 1 gene 2 gene 3 gene 4 DNA trp promoter operator repressor trp repressor protein = INACTIVE trp trp trp conformational change in repressor protein makes it ACTIVE! trp repressor tryptophan trp tryptophan – repressor protein Complex = ACTIVE

Inducible lac operon SLIDE FROM: Kim Foglia VIDEO codes for enzymes for lactose digestion lac lac RNA lac repressor TATA polymerase When lactose is present, binds to lac repressor protein & triggers repressor to release DNA – induces transcription gene 1 gene 2 gene 3 gene 4 1 2 3 4 enzyme 1 enzyme 2 enzyme 3 enzyme 4 m. RNA promoter Digestive pathway model operator conformational change in repressor protein makes it INACTIVE! repressor lac repressor DNA repressor protein =ACTIVE lactose – repressor protein Complex = INACTIVE

Using REPRESSORS to TURN OFF genes = NEGATIVE CONTROL REPRESSIBLE and INDUCIBLE operons ARE BOTH TYPES OF NEGATIVE CONTROL ! ! http: //3. bp. blogspot. com/-t. Ar. Opdc. SKl. Q/VDy. OFD 4 h. J 8 I/AAAABw 8/r. Eax. BPVNf-g/s 1600/Electical%2 BLight%2 Bswitch. . . cartoon. jpeg

Using ENHANCER REGIONS and ACTIVATORS/INDUCERS to TURN ON genes = POSITIVE CONTROL http: //cdn. xl. thumbs. canstockphoto. com/canstock 8046278. jpg

POSTIVE CONTROL of Lactose operon What happens when concentration of glucose is LOW? LOW GLUCOSE → HIGH c. AMP GLUCOSE IS FOOD OF CHOICE VIDEO Catabolite Activator Protein c. AMP makes CAP active; starts transcription Image from: http: //image. slidesharecdn. com/18 regulationofgeneexpression-130613012903 -phpapp 02/95/18 -regulation-of-gene-expression-15 -638. jpg? cb=1371087103

POSTIVE CONTROL of Lactose operon What happens if BOTH GLUCOSE AND LACTOSE are present? GLUCOSE IS FOOD OF CHOICE Catabolite Activator Protein Repressor is inactive but CAP activator is not activated Gene is unable to turn on at significant rate Image from: http: //image. slidesharecdn. com/18 regulationofgeneexpression-130613012903 -phpapp 02/95/18 -regulation-of-gene-expression-15 -638. jpg? cb=1371087103

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

ACTIVATORS BIND TO ENHANCER region Image from: https: //cellularphysiology. wikispaces. com/file/view/18_09 Activator. Action_3 -L. jpg/465203668/18_09 Activator. Action_3 -L. jpg

MAKE A CONNECTION WHERE DO ACTIVATOR proteins come from? Images from http: //images. slideplayer. com/1/273672/slides/slide_49. jpg http: //image. slidesharecdn. com/45 lecturepresentation-101204060035 -phpapp 01/95/chapter-45 -textbook-presentation-33 -728. jpg? cb=1291442560

ACTIVATED ENHANCERS attach to TRANSCRIPTION FACTORS and FOLD DNA back onto itself Image from: https: //cellularphysiology. wikispaces. com/file/view/18_09 Activator. Action_3 -L. jpg/465203668/18_09 Activator. Action_3 -L. jpg VIDEO

RNA POLYMERASE attaches to TRANSCRIPTION INTIATION COMPLEX to start transcription (GENE is turned ON!) Image from: https: //cellularphysiology. wikispaces. com/file/view/18_09 Activator. Action_3 -L. jpg/465203668/18_09 Activator. Action_3 -L. jpg

Different genes have different enhancer regions and are controlled by different activators Image from: http: //image. slidesharecdn. com/18 regulationofgeneexpression-130613012903 -phpapp 02/95/18 -regulation-of-gene-expression-35 -638. jpg? cb=1371087103

DIFFERENT ENHANCER sequences can TURN ON a gene in DIFFERENT KINDS of cells at DIFFERENT TIMES. Image from: https: //cellularphysiology. wikispaces. com/file/view/18_09 Activator. Action_3 -L. jpg/465203668/18_09 Activator. Action_3 -L. jpg