Lecture Four Handout (pdf): What Are Genes & How Do They Work

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HC70A, PLSS530, & SAS70A Spring 2015 Genetic Engineering in Medicine, Agriculture, and Law Professors Bob Goldberg, Channapatna Prakash, & John Harada…
HC70A, PLSS530, & SAS70A Spring 2015 Genetic Engineering in Medicine, Agriculture, and Law Professors Bob Goldberg, Channapatna Prakash, & John Harada Lecture 4 What Are Genes & How Do They Work: Part Two Course Administratorp 5’ 3’ 5 ’ 3’ 1.  What Are the Properties of Genes? a)  Replication b)   Direct the Production of Traits c)  Universality d)   Stability 2.  What is the Evidence For DNA Being the Genetic Material? a)  Griffith Experiment b)   Avery et al. Experment c)  How Does the Avery Experiment Satisfy the Predictions of DNA as the Genetic Material? 3.  Transformation Can Be Done Universally & Is the Foundation of Genetic Engineering 4.  Began Structure of DNA 5.  Demonstration a)  Bacterial “Cloning” Last Tuesday’s Lecture: What Are Genes & How Do They Function - Part One THEMES 1.  What is the Anatomy of a Gene? 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!-It’s in the DNA Sequences- What Are the Implications For Genetic Engineering? Reflections on The Double Helix DNA is a Double Helix of Two Complementary Chains of DNA Wound Around Each Other 1.  Complementary Strands 2.  A=T and G=C (Four Bases) 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!) 8.  No Constraint on Sequence (4n=n # sequences) 9.  DNA has dimensions (Know # bp Know Length: 20Å diameter,3.4Å/bp, 10bp/turn) 10. Sequence = Biology Watson and Crick, Nature, 1953 5’ 3’ 3 ’ 5’ 5 ’ 3’ 5’ 3’ A Chromosome Contains One (or Two!!) Continuous DNA Molecule(s) DNA in Human & Eukaryotic Chromosomes is Linear and Wrapped Around Proteins Called Histones! DNA in Most Bacteria is Circular! A Chromosome Contains Many Genes That Work As Individual Units (How Know?) 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 5’ 3’ Coding Template 3’ 5’ What delineates each gene? Notice sequence of each gene 5’ 3’ 5’ 5’ 3’ 3’ 5’ 3’ Function 3 Function 2 Function 1 N C C C N N Note sequence of each protein Evidence? Genes Reside at Specific Chromosomal Locations Linear DNA How Know? •  Note Marker Bands - What are these? •  How Know Gene Positions? Chromosome Number? Circular DNA How Know? Map of E. coli Genome All Genes Linked On Same DNA A ll Ge ne s Li nk ed o n Sa m e Ch ro m os om e or P ie ce o f DN A Gene Loci Can Be Mapped and Visualized Gene Position = Locus = Unique DNA Sequence Alleles Are Different Forms of the Same Gene That Arise By Mutation & Can be Made in a Laboratory By Modern Genetic Engineering! Different Alleles at Same Position on Chromosome Alleles Reside at the Same Position on a Chromosome Gene Engineering Can Generate New Forms of Alleles of a Gene and, therefore, Results in More Genetic Diversity Different Genes All Linked on One Chromosome Each Phenotype is a MARKER for the Allele & It’s Position on the Chromosome Genetically! (Many Alleles!) Organization of Genes on Human Chromosome 22 Gene 1 One Large Gene! Genes Are Defined/ Precise Regions of DNA Genes Act As Individual Units? How Know? Design an Experiment!! Gene 2 Gene 3 Gene 4 5’ Structural 3’ A Conceptualized Gene Sense Strand (Genetic Code) Transcribed Strand or Nonsense Strand Beginning End Complementary to Transcribed Strand or SAME Sequence as Sense Strand Only Know the Structure of a Gene Because of the Invention of Recombinant DNA Technology – Why? 5’ 3’ Gene 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 5’ END 3’ 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 5’ END 3’ 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 CELLS ! COMPLEMENTARY TO TRANSCRIBED STRAND =TEMPLATE FOR RNA The Detailed Anatomy of a Gene Note: mRNA Sequence = Sense Strand Sequence Marks the Sense Strand “Simple” Gene Anatomy Reviewed Genes Function As Independent Units - Design Experiment to Show! “Everything” Follows the Double Helix & Its Rules - Anti-parallel Chains & Complementary Base Pairing! 1.  Sense Strand = Genetic Code 2.  Sense Strand = 5’ ž 3’ Direction (all DNA sequences specified 5’ ž 3’) 3.  Anti-Sense Strand = Complement of Sense Strand & is Transcribed Strand 4.  mRNA = Same Sequence As Sense Strand & Complementary to Antisense Strand 5.  mRNA = 5’ ž 3’ 6.  Switch Turns Gene On - Not Transcribed But Upstream of Coding Region
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