Transcript Bio1100Ch20
CHAPTER 20 DNA TECHNOLOGY AND GENOMICS • Recombinant DNA - genes from two different sources - are combined in vitro into the same molecule. • Genetic engineering- the direct manipulation of genes for practical purposes. • Biotechnology -the manipulation of organisms or their components to make useful products. • Pre 1970s- • microbes to make wine and cheese • selective breeding of livestock • Post 1970s- Move individual genes into the organism of choice. • DNA technology ranges from agriculture to criminal law, but its most important achievements are in basic research. • One basic cloning technique begins with the insertion of a foreign gene into a bacterial plasmid. Fig. 20.1 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 1. The human genome project • Human Genome Project-begun in 1990. • Determine complete nucleotide sequence of each human chromosome. • An international, publicly funded consortium has proceeded in three phases: genetic (linkage) mapping, physical mapping, and DNA sequencing. • The genomes of several other organisms important to biological research have also being mapped. • These include E. coli, yeast, fruit fly, and mouse. • J. Craig Venter decided in 1992 to try a one-step whole-genome shotgun approach. Consortium’s three stage approach Venter’s whole genome approach Fig. 20.13 1. Genetic map 2. Physical map 3. DNA sequence DNA sequence • 1995- Venter reports the complete sequence of a bacterium. • 2000- Venter’s private company, Celera Genomics, finishes the sequence of Drosophila melanogaster • 2001-Celera and the public consortium separately announced sequencing over 90% of the human genome. • By mid-2001, the genomes of about 50 species had been completely (or almost completely) sequenced. •Include yeast, a nematode, a plant and many bacteria 2. DNA microarrays • Automation has allowed scientists to detect and measure the expression of thousands of genes at one time using DNA microarray assays. •1000s of copies of each gene are fixed on glass slide •The fragments are tested for hybridization with various samples of fluorescently-labeled cDNA molecules. Fig. 20.14a • Spots where any of the cDNA hybridizes fluoresce with an intensity indicating the relative amount of the mRNA that was in the tissue. Expression of 3,600 genes can be tested using a single 0.5 inch grid Fig. 20.14b • Proteomics- the systematic study of full protein sets (proteomes) encoded by genomes. • Genomics and proteomics are giving biologists an increasingly global perspective on the study of life. • Bioinformatics- the application of computer science and mathematics to genetic and other biological information 3. What is a “bad” gene?? Most of human diversity is in the form of single nucleotide polymorphisms (SNPs), single basepair variations. • In humans, SNPs occur about once in 1,000 bases, meaning that any two humans are 99.9% identical. • The locations of the human SNP sites will provide useful for : • studying human evolution • identifying disease genes • genes that affect susceptibility to diseases, toxins or drugs What is a single nucleotide polymorphism? Person 1……AGACGTAGACAGATCGTCCCAGAGATTAG AGGACATGGACAGAGATGGCAGAGCTCTCTCT TTTAGAGTACATGATACGATACAGATCAGATCA GATACGATACAGTACAGTAGATACGATATACAGF AGACTAGCAGTAGACGATRGACGTCTCGCGCG CGCGCGATCGTAGCTGATCGATGCAGTCAGT….. Person 1……AGACGTAGACAGATCGTCCCAGAGATTAG AGGACATGGACAGAGATGGCAGAGCTCTCTCT TTTAGAGTACATGATACGAGACAGATCAGATCA GATACGATACAGTACAGTAGATACGATATACAGF AGACTAGCAGTAGACGATRGACGTCTCGCGCG CGCGCGATCGTAGCTGATCGATGCAGTCAGT….. Perhaps person , but not person 2 is predisposed to breast cancer What is gene therapy? How successful is gene therapy? How was the constortium’s approach to human genome sequencing different from Craig Venter’s approach? 10,000 bp of DNA 4. Gene Therapy • Techniques for gene manipulation hold great potential for treating disease by gene therapy. • A normal allele is inserted into somatic cells of a tissue affected by a genetic disorder. • Despite “hype” in the news media over the past decade, there has been very little scientifically strong evidence of effective gene therapy. • Even when genes are successfully and safely transferred and expressed in their new host, their activity typically diminishes after a short period. • One death in 1999 completely halted US trials • Gene therapy poses many technical questions. • Right amount at right time • What if transferred gene inserts into a required gene? • Ethical and social questions. • Some critics suggest that this tampering is wrong. • Will it lead to eugenics? • should we treat human germ-line cells to correct the defect in future generations. 5. DNA technology in forensics • Violent crimes- blood, semen, or traces of other tissues may be left at the scene • blood type or tissue type can only exclude a suspect. • DNA fingerprints can be used forensically to presence evidence to juries in murder trials. Fig. 20.17 6. DNA technology in environmental applications • Genetically engineered microbes that can extract heavy metals from their environments - cleaning up highly toxic mining wastes. • New microbes that can degrade other harmful compounds are being engineered. 7. DNA technology in agriculture •Transgenic organisms with genes from another species –to grow faster or larger Pharmaceutical “factories” – human insulin produced in pigs Fig. 20.18 • Genetic engineering is quickly replacing traditional plant-breeding programs. • 50% of American soybeans and corn grown from genetically modified seeds. • Contain genes for resistance to weed-killing herbicides or to infectious microbes and pest insects. • Gene transfer to improve the nutritional value of crop plants. •Introduce B-carotene (a vitamin A precursor) into transgenic rice to prevent vision impairment in third world Fig. 20.20 8. DNA technology raises important safety and ethical questions • The power of DNA technology has led to worries about potential dangers. • Create hazardous new pathogens? • AIDS virus? • Many countries carefully monitor laboratories • Accidental release • Bioterrorism • Is the Saddam Hussein regime in Iraq a threat? • Recent anthrax-by-mail scheme • Small pox • Most public concern centers on genetically modified (GM) organisms used in agriculture. • “GM organisms” have acquired one or more genes (perhaps from another species) by artificial means. • Genetically modified animals are still not part of our food supply, but GM crop plants are. • In Europe, safety concerns have led to pending new legislation regarding GM crops and bans on the import of all GM foodstuffs. • In the United States and other countries the labeling of GM foods is now being debated. • To date there is little good data either for or against any special health or environmental risks posed by genetically modified crops. • As with all new technologies, developments in DNA technology have ethical overtones. • Who should have the right to examine someone else’s genes? • How should that information be used? • Should a person’s genome be a factor in suitability for a job or eligibility for life insurance? • The power of DNA technology and genetic engineering demands that we proceed with humility and caution.