HC70A & SAS70A Winter 2009 Genetic Engineering in Medicine, Agriculture, and Law Professors John Harada & Bob Goldberg Lecture 3 What Are Genes & How Do They Work: Part Two The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.Algae genes for chlorophyll biosynthesis have been incorporated into the sea slug genome – Horizontal Gene Transfer! Chloroplasts are normally found only in plant cells1. What Are the Functions of Genes? 2. What Is Gene & Genetic Diversity 3. What is the Evidence For DNA Being the Genetic Material a) Griffith & Avery et al. Experiments b) Modern Genetic Engineering Experiments 4. Structure of DNA 5. Genes & Chromosomes in Prokaryotes & Eukaryotes Review of Last Tuesdayʼs Lecture: What Are Genes & How Do They Work - Part OneGene Action Leads to Specific Traits – Genotype Specifies Phenotype 1. Replication 2. Gene Action 3. Cell Function (Trait) Genetic Engineering Alters Cell Function By Changing the Genotype How is this Demonstrated Experimentally? Design an Experiment! 5ʼ 3ʼ 5ʼ 3ʼ 3ʼ 5ʼ Genotype Phenotype Collection of Genes Collection of TraitsAlleles Account for Variability in Traits – Breeding Takes Advantage of this Natural Genetic Variability This Genetic Variability Arose Spontaneously By RARE Mutations Mendelʼs Traits Resulted from Different Alleles of the Same GeneThe Griffiths Experiment The Transforming Principle 1 2 3 4Experiments by Avery et al. Showed that DNA is the Genetic Material When Dnase Destroyed DNA There Was No Transformation & Only Rough Cells Were Found In CultureAll Organisms Can Be Transformed!! Genetic Engineering Has Come a Long Way Since Griffiths Experiments in 1928!! Streptococcus pneumoniaeDNA Structure 1. Complementary Strands 2. A=T and G=C 3. Sequence of Strands Differ 4. Bases to Interior 5. Phosphate-Sugar Backbone on Exterior 6. DNA Strands in Opposite Direction (Only Way Helix Fits) 7. Sequence of One Chain Automatically Specifies Sequence of Complementary Chain (Basis of Replication!) Watson and Crick, Nature, 1953 5ʼ 3ʼ 3ʼ 5ʼ 5ʼ 3ʼ 5ʼ 3ʼGenes Reside at Specific Locations Linear DNA Note Bands - What are these? How Know Gene Positions? Chromosome #? Circular DNA Map of E. coli GenomeFigure 4-15 Molecular Biology of the Cell (© Garland Science 2008) Organization of Genes on Human Chromosome 22 Gene 1 One Gene! Genes Are Defined/Precise Regions of DNA Genes Act As Individual Units? How Know? GloFish Experiment! Genetic Engineering AntibioticR Gene 2 Gene 3 Gene 4 5ʼ Structural 3ʼTHEMES 1. What is the Function of a Gene-Review? 2. How Are Genes Regulated - Switched On & Off? 3. How Does DNA Replication Occur? 4. What is the Polymerase Chain Reaction (PCR) and How is PCR used? 5. How Do Mutations Occur? 6. How Can Pedigrees Be Used To Follow the Inheritance of Mutant Genes? 7. How Do Mutations Change Phenotypes? 8. What is the Colinearity Between Genes & Proteins (how does DNA→protein)? 9. What Is the Genetic Code? 10. How Do Gene Expression Processes Differ in Eukaryotes & Prokaryotes? 11. How Can Splicing Cause One Gene To Specify Several Different Proteins? 12. Yo!-Itʼs in the DNA Sequences- What Are the Implications For Genetic Engineering?A Conceptualized Gene Sense Strand Transcribed Strand Beginning End On SwitchGene X Beginning End T A T A A T A G C T C G A A C A T T T T TRANSCRIBED STRAND SENSE STRAND 5ʼ END 3ʼ END A T A T T A T C G A G C T T G T A A A A Genetic Code (Function) START “SWITCH” OR PROMOTER TERMINATION “SWITCH” Downstream Next Gene Upstream Next Gene 5ʼ END 3ʼ END A G C U C G A A C P OH mRNA X START TRANSCRIPTION END TRANSCRIPTION CONTROLS When & where a gene becomes active? UNIQUE CELL TYPES ! COMPLEMENTARY TO TRANSCRIBED STRAND = TEMPLATE FOR RNA A Gene is a Specific DNA Sequence that Directs the Expression of a Unique Trait Note: mRNA Sequence = Sense Strand SequenceA Chromosome Contains Many Genes That Work As Individual Units Position of Genes 1, 2, & 3 in chromosome Discrete Units! VERY IMPORTANT CONCEPT! COLINEARITY BETWEEN GENE SEQUENCE AND PROTEIN SEQUENCE Notice- Each gene, mRNA, & protein has a unique order/sequence of monomeric units Central Dogma ∴ Genes -> Functions in Cells via Proteins Cells duplicate & stay the same -> DNA replication 5ʼ 3ʼ Coding Template 3ʼ 5ʼ What delineates each gene? Notice sequence of each gene 5ʼ 3ʼ 5ʼ 5ʼ 3ʼ 3ʼ 5ʼ 3ʼ Function 3 Function 2 Function 1 N C C C N N Note sequence of each protein Evidence?A “Simple” Gene Reviewed Genes Function As Independent Units – WHY IMPORTANT FOR GENETIC ENGINEERING? “Everything” Follows the Double Helix & Its Rules - Anti-parallel Chains & Complementary Base Pairing! 1. Sense Strand = Genetic Code 2. Sense Strand = 5ʼ! 3ʼ Direction (all DNA sequences specified 5ʼ! 3ʼ) 3. AntiSense Strand = Complement of Sense Strand & is Transcribed Strand 4. mRNA = Same Sequence As Sense Strand & Complementary to AntiSense Strand 5. mRNA = 5ʼ! 3ʼ 6. Switch Turns Gene On - Not Transcribed But Upstream of Coding RegionControl Switches Are Unique DNA Sequences & Can Be Cloned AND used to Re-Engineer Organisms!! Switches Act Independently of Gene!! “Control” Switch “On” SwitchSwitches Control Where & When A Gene Is Active → Unique Functions → Unique Cell Types Insulin Gene Hemoglobin Gene Antibody Genes1. They Can Be Cloned & “Shuffled” & Engineered Creating New Genes That Have No Counterparts in Nature. c Genetic Engineering 2. These New Genes Can Be Transcribed in New Cell Types (Switch Change) &/or Organisms &/or Both. (e.g., Human Genes in Plant Seed) ò Human Genes Ë Plant Seed Switch 3. All Genes are Regulated & Controlled by Switches. Genome Projects Reveal Both The Genes & The Switches & Wiring Together of All Switches in Gene. c Program of Life From Birth to Death THE GENE AND SWITCHES ARE UNIQUE DNA