Genetic Engineering: Benefits and Concerns

1. Golden Riceor Frankenfood? • Scientists transferred daffodil genes into rice • Rice with beta-carotene may help prevent vitamin A deficiencies • Opponents fear unforeseen consequences of creating genetically modified organisms

2. Genetic Changes • Humans have changed the genetics of other species for thousands of years • Artificial selection of plants and animals • Natural processes also at work • Mutation, crossing over

3. Genetic Engineering • Genes are isolated, modified, and inserted into an organism • Made possible by recombinant DNA technology • Cut up DNA and recombine pieces • Amplify modified pieces

4. Discovery of Restriction Enzymes • Hamilton Smith studied how bacterium Haemophilus influenzae cut invading viral DNA • Discovered that bacteria have an enzyme that chops up viral DNA

5. Specific Cuts • Restriction enzymes cut DNA at a specific nucleotide sequence • Cuts leave “sticky ends” on DNA fragments that pair with matching cuts

6. Making Recombinant DNA 5’ G A A T T C 3’ C T T A A G one DNA fragment another DNA fragment 5’ G A A T T C 3’ 5’ C T T A A G 3’

7. Making Recombinant DNA nick 5’ G A A T T C 3’ 3’ C T T A A G 5’ nick DNA ligase action G A A T T C C T T A A G

8. Using Plasmids • Plasmid: a small circle of bacterial DNA • Foreign DNA inserted into plasmid • is replicated and distributed along with plasmid • Plasmid becomes a cloning vector • delivers DNA into another cell

9. Cloning Vectors

10. Using Plasmids e The DNA fragments and plasmid DNA are mixed with DNA ligase. a A restriction enzyme cuts a specific base sequence everywhere it occurs in DNA. b The DNA fragments have sticky ends. f The result? A collection of recombinant plasmids that incorporate foreign DNA fragments. c The same enzyme cuts the same sequence in plasmid DNA. d The plasmid DNA also has sticky ends g Host cells that can divide rapidly take up the recombinant plasmids. Fig. 11-3, p.164

11. Gene Libraries • Cells that host fragments of cloned DNA • Genomic library

12. Where am I? • 123 Devilbiss • Biology 101 • SU • US • Earth

13. DNA Sequencing • Order of fluorescent bands indicates DNA sequence

14. Polymerase Chain Reaction • Sequence to be copied is heated • Primers are added and bind to ends of single strands • DNA polymerase uses free nucleotides to create complementary strands • Doubles number of copies of DNA

15. DNA heated to 90°– 94°C primers added to base-pair with ends mixture cooled; base-pairing of primers and ends of DNA strands DNA polymerases assemble new DNA strands Polymerase Chain Reaction double-stranded DNA to copy

16. mixture cooled; base-pairing between primers and ends of single DNA strands DNA polymerase action again doubles number of identical DNA fragments Polymerase Chain Reaction mixture heated again; makes all DNA fragments unwind

17. DNA Fingerprints • Unique array of DNA fragments • Inherited from parents in Mendelian fashion • Even full siblings can be distinguished from one another by this technique

18. Analyzing DNA Fingerprints • DNA is separated by gel electrophoresis • Pattern of bands is used to • Identify or rule out criminal suspects • Identify bodies • Determine paternity

19. A DNA Fingerprint

20. DNA Sequence Data • Evolutionary trends • Potential therapies for genetic diseases • Data bases using computer technology

21. Genetics in Practice • Genetic engineering is used to change genetic makeup of organisms • Genes transferred between species (Transgenic organisms) • Genes modified and reinserted into same species

22. Transgenic Plants • Contain DNA from another species • New genes make crop plants less vulnerable to disease and pests • Use bacterial cloning vectors to insert foreign gene (Ti plasmid)

23. Transgenic Cotton • Resistant to herbicides • Insecticide gene

24. Genetically Engineered Bacteria • Produce medically valuable proteins • Breakdown environmental contaminants • Designed to survive only under narrow conditions

25. Transgenic Animals • Early experiments in mice • Injection of rat gene corrected a growth-hormone deficiency • Injection of human growth-hormone gene produced giant mice • Human genes are now routinely transferred into animals to produce human proteins for use as drugs

26. Genetically Modified Animals

27. Gene Therapy For SCID-X1 • Designed to cure “bubble babies” • Immune system can’t fight infection

28. Gene Therapy For SCID-X1 • Retrovirus inserts normal allele into cultured stem cells • Modified stem cells returned to child’s bone marrow • Successfully created immune function • Also caused leukemia in some children

29. Who Gets Enhanced? • Eugenic engineering • Selecting for “desirable” human traits • How should we use gene therapy? • Who should decide what genetic traits can or should be altered?

30. Xenotransplantation • Human organs are in short supply • Pig organs are similar, but human body rejects them as foreign • Scientists work to knockout pig genes that trigger rejection • Can interspecies transplants introduce new diseases to humans?

31. “Frankenfood” • Genetically engineered foods are widespread in the US • Cut costs, reduce herbicide use, enhance yields • What effect will they have on humans and ecosystems?

32. Transgenic Mouse • With genes for fluorescent protein