Purpose of this Lab Learn how to insert a gene into bacteria (Heat Shock) Analyze how a gene can transform an organism and express that gene Provide evidence that bacteria can take in foreign DNA in the form of a plasmid Reinforce the following process: DNA RNA Protein Trait Observe how genes are regulated
Applications of Genetic Transformation Used in many areas of Biotechnology –Agriculture (pests, frost, & drought) –Bacteria (oil spills) –Gene therapy (sick cells into healthy cells) –Medicine (produce insulin & hormones)
Key Terms to Know DNA: Plasmid Bacteria: E. coli (strain: HB101K-12) Growth media: LB Broth (Luria & Bertani) Ampicillin:Antibiotic kills bacteria “amp” Arabinose:Sugar source for energy & carbon Heat shockProcess that increases permeability of the cell membrane to DNA GFP:Green Fluorescent Protein (w/UV)
The Genes of Interest Ampicillin resistance Gene regulation proteins-activate the GFP gene when arabinose is present GFP: Green Fluorescent Protein -originally isolated from the jellyfish: Aequorea victoria
Chapters 18 & 19 Bacteria Viruses & Operon Systems
Key Topics and Text Pgs to Review TopicPgs. Bacteria:Genetic recombination 346-350 Plasmids & Conjugation Transformation (Lab #8) Transposons: 351-352 Lac Operon System 353-356 RegulatingGene Expression Viruses: DNA, RNA (retroviruses) 338-342 Lytic & Lysogenic Cycle 337-339
Relative size Differences between of Viruses, Prokaryotes, and Eukaryotes
Transformation Uptake of foreign DNA from the environment What we did in our lab (pGLO plasmid) Requires unique cell-surface proteins on the that can recognize similar strands of DNA, bind to it, and allow uptake.
Expected Results PLATESOBSERVATIONS +pGlo LB/amp Many colonies with white appearance Transformation observed (resistance to amp) NO fluorescence (No arabinose present) +pGlo LB/amp/ara Many transformed white colonies Fluoresce bright green under UV light -pGlo LB/amp (CONTROL) No Bacterial growth present on the plate No transformation -pGlo LB only (CONTROL Bacteria present with whitish colonies (regeneration of the starter plate)
Introductory Questions # 1)Briefly explain the differences between Transformation, Conjugation, and Transduction. How are these three processes the same? (pgs. 348-349) 2)How is an “F plasmid” different from an “R plasmid”? 3)What are transposable elements and what do they do?
Introductory Questions # 1)Name the two scientists that discovered the Lac operon system. 2)How are repressible operons different from inducible operons? Give an example of each. 3)What is the difference between an operator and a promoter? 4)Name three example of a virus that has DNA as its genetic material and three examples of Viruses with RNA as its genetic material. 5)Briefly explain what a vaccine is and what it does.
Insertion Sequences & Transposable Elements Always a part of of chromosomal or plasmid DNA Sometimes called “jumping genes”-never detach A single gene for coded for:transposase Inverted sequences are on each side of an insertion sequences. Observed in bacteria only. –See pg. 352 Specialized plasmids are constructed using these sequences.
Jacob & Monod Discovered Lac Operon – Nobel Prize for Discovering Control of Gene Expression
Specialized Genes Operator = "on/off" switch for operon Regulator = makes repressors to turn off an entire operon Repressor = Binds to operator, turn off gene expression Inducer = Joins with an active repressor, inactivates it Co-repressor = Joins with inactive repressor, converts it to active
OPERON THEORY Operon = group of structural genes regulated as a unit Several genes controlled by an operator site
Operon Complex RNA Polymerase must bind to the promoter site and continue past the operator site to transcribe mRNA
INDUCIBLE Operons Usually “OFF” - to turn ON: –INDUCER needs to bind to an active repressor and inactivate it –RNA Polymerase can then bind and transcribe mRNA Ex. Lac operon is an inducible operon
Lac Operon Summary Beta- Galactosidase can then be made
Repressible Operons Usually “ON” - to turn OFF: –Co-repressor needs to bind to an inactive repressor and activate it –RNA Polymerase then cannot bind and transcribe mRNA Ex. trp operon is a repressible operon: -trancription is usually on -inhibited only by tryptophan (corepressor)
Classic Example of Theory Splitting of a disaccharide LACTOSE molecule within E. coli (Lac Operon) –TWO molecules needed to bind to promotor site to induce transcription of lactose-splitting beta- galactosidase One molecule = complex of cyclic AMP (cAMP) & cyclic AMP binding protein (CAP) One molecule = RNA polymerase
Lac Operon Lactose ONLY used when glucose is not present in large quantities When glucose is present, cAMP levels are low, cAMP cannot bind to CAP and initiate enzyme production
Lac Operon In absence of glucose, cAMP levels are HIGH, binding to CAP can occur Beta-Galactosidase is made
Lac Operon RNA polymerase only binds efficiently when cAMP-CAP complex is in place Lac Operon = an INDUCIBLE Operon Lactose = an INDUCER –Binds to repressor and inactivates it
Operons Inducible (lac operon): lactose metabolism lactose not present: repressor active operon off no transcription for lactose enzymes lactose present: repressor inactive operon on inducer molecule inactivatesprotein repressor (allolactose) transcription is stimulated when inducer binds to a regulatory protein
Introductory Questions # 1)Why are transposons called “jumping genes”? What purpose do the insertion sequences play? 2)What is the difference between an oncogene and a tumor repressor gene?
Molecular Biology of Cancer Oncogene cancer-causing genes Proto-oncogene normal cellular genes How? 1-movement of DNA; chromosome fragments that have rejoined incorrectly 2-amplification; increases the number of copies of proto-oncogenes 3-proto-oncogene point mutation; protein product more active or more resistant to degradation Tumor-suppressor genes changes in genes that prevent uncontrolled cell growth (cancer growth stimulated by the absence of suppression)