Advancements in Genetic Engineering: From Selective Breeding to DNA Sequencing

1. Chapter 15: Genetic Engineering Section 15-1: Selective Breeding

2. Selective Breeding • When humans allow only organisms with “wanted” or “desired” characteristics to produce the next generation • Technique used for thousands of years to produce new varieties of cultivated plants and domesticated animals • Two methods: hybridization and inbreeding

3. Hybridization • Crossing dissimilar individuals to bring together the best characteristics of both organisms • Hybrids often hardier than either parent • Example: crossing a disease resistant plant with one that produces a lot of food

4. Inbreeding • Continued breeding of individuals with similar characteristics • Maintains desirable characteristics in a line of organisms • Example: pure bred dogs and cats • Can be risky – higher chance of recessive alleles pairing, genetic defects

5. Increasing Variation • Scientists who manipulate organisms’ genetic makeup are using biotechnology – the application of a technological process , invention, or method to living organisms • Types of biotechnology include selective breeding, increasing mutation rates, using drugs to create polyploid plants, and others

6. Bacterial Mutations • Using radiation or chemicals (mutagens) can increase the rate of mutation • Breeders can create mutants with beneficial characteristics • Example: oil digesting mutant bacterial strains are used to help clean up oil spills; working on bacteria that can clean up radioactive substances or metal pollution

7. Polyploid Plants • Drugs that prevent chromosome separation in meiosis are useful in plant breeding, to create polyploid plants that are larger and stronger than the normal diploids • Many important crop plants are polyploid

9. Chapter 13 – Recombinant DNA and Genetic Engineering College Prep Biology Mr. Martino

10. Introduction • Gene Therapy: transfer of one or more modified genes into an individual’s cells • Correct genetic defect • Boost immune system • Recombinant DNA Technology: science of cutting and recombining DNA from different species • Genes are then placed into bacterial, yeast or mammalian cells and replicated • Genetic Engineering: genes are isolated, modified, and inserted back into a cell • also called biotechnology

11. 15.1 Making Recombinant DNA • Restriction enzyme: enzyme that chops up DNA at a specific sequence • Bacterial • Viral defense mechanism • May cut a DNA strand a few times • Helpful in studying DNA • Produces “sticky ends” which may pair with other DNA • Genome: all the DNA in a haploid number of chromosomes for each species

12. Plasmids: small circle of DNA • In bacterial cells • Insert foreign DNA (gene) into and put back in bacteria – reproduces naturally making a DNA clone • Cloning vector: plasmid used to accept foreign DNA and replicate it • Reverse transcriptase: enzyme from RNA viruses that perform transcription in reverse (RNA to DNA) • cDNA: (copied DNA) mature mRNA transcript that has already been spliced • Bacteria cannot remove introns and splice exons • Reverse transcriptase makes DNA from mRNA to insert into plasmid

13. 15.2 PCR – Polymerase Chain Reaction • PCR: a fast method of amplifying (making lots of copies) DNA • DNA isolated, mixed with DNA polymerase, nucleotides, and some other good stuff • Produces 2 daughters • Daughters replicate, etc. • 1 DNA molecule generates 100 billion in a few hours • Used in evolution research, analyze DNA from fossils, analyze embryos, court cases

14. 15.3 DNA Fingerprints • No two people have exactly identical DNA • Except identical twins • DNA Fingerprint: unique set of DNA fragments • Used to determine paternity, solve crimes, etc. • 99.9% all human DNA is identical • Focus on highly variable areas of tandem repeats • Mutations occur within families and are more common in these areas

15. Gel electrophoresis: uses an electric current to force DNA fragments through a gel • DNA is negative • Size of fragment determines how far it migrates • The fewer tandem repeats the farther it travels • Differences in homologous DNA sequences resulting in fragments of different lengths are restriction fragment length polymorphisms (RFLP’s)

17. 15.4 DNA Sequencing • 1995 – entire DNA sequence for a bacterium was determined • 4/25/03 – Human genome completed • Several bacteria, yeast, Drosophila,C. elegans - worm, Arabidopsis - weed, Mickey…a mouse, just completed 3/31/04 – a rat) • Used a sequencing machine

18. 15.5 Isolating Genes • Genomic Library: set of DNA fragments from an organism’s genome • Complementary RNA sequence can be synthesized with a radioactive isotope tag called a probe • Used to find a specific gene • Tags the gene whenever encountered • Gene may then be isolated

19. 15.6 Using the Technology • True human insulin is now manufactured • Also somatotropin (growth hormone), blood-clotting factors, hemoglobin, interferons (cancer research), and various other drugs and vaccines • Bacteria for oil spill clean up and other environmental pollution

20. 15.7 Designer Plants • Genetically engineered plants have been developed for pharmaceuticals, herbicide, pest, and disease resistance, larger and tastier plants, fruits, and vegetables with greater yields • Corn, cotton, potato, soy bean, etc

21. 15.8 Gene Transfers in Animals • Cloning holds promises for future • Clone organs and tissues • Possibly modify animals to be more disease resistant and produce greater quantities of products • Not currently occurring in farm animals

25. 1997 – the first animal was cloned – Dolly a lamb • 1. Remove nucleus from cell • 2. Transfer nuclei from desired cells into unfertilized eggs • 3. Implant the “zygote” into surrogate mother • Since Dolly – we have cloned mice, rats, cows, cats, mules, horses, and Rhesus monkeys along with a couple of endangered animals

27. Human Genome • HGP – an int’l effort to map and sequence all human genes • 15 countries started 11/1/90 and finished 4/25/03 (50 years after Watson & Crick paper published) • 1. Genome – only 30,000 genes so it took less time • Includes mapping & sequencing of other species for comparison • 2. RNA transcription – more difficult since 30,000 genes code for 80,000 proteins due to alternative splicing • 3. Proteome – quest for every human protein

28. 15.9 Who Gets Enhanced? • HGP already has an ethics committee due to insistence of James Watson • HGP needs to be used to help people and must be regulated by laws • Must prevent invasion of privacy and discrimination by insurance companies, employers,etc. • Must prevent Eugenics: purging of “undesirable” traits from human population (Hitler) • Science provides society with knowledge and opportunities – society requires rules and constraints to prevent abuse

29. Chapter 15: Genetic Engineering Section 15-3: Applications of Genetic Engineering

30. Agriculture and Industry • Genetic engineering used to improve products we get from plants and animals • Could lead to better, less expensive, more nutritious food, and safer manufacturing processes

31. GM Crops • Genetically modified plants since 1996 • Example: adding bacterial genes that produce Bt toxin - kills insects • No pesticides needed • Higher crop yields • Resistance to herbicides, viral infections, rot and spoilage • Some being made to produce plastics

33. GM Animals • 30% of milk produced by cows modified with hormones that increase milk production • Pigs that produce leaner meat , high levels of omega-3 • Salmon with extra growth hormone to make them grow quicker • Canada – goats that produce silk • Goat milk with antibacterial enzymes

34. GM Animals • Scientists hoping to clone transgenic animals to increase food supply and save endangered species • 2008 – gov’t allowed sale of meat and milk from cloned animals • Avoid complications of traditional breeding, duplicate exactly

35. Preventing Disease • Making more nutritious plants • Producing antibodies to fight disease • Make proteins we need

36. Medical Research • Transgenic animals used as test subjects • Study defective genes, disease progression • Conduct drug tests

37. Treating Disease • Recombinant DNA technology used to make human proteins to treat disease – human growth hormone, insulin, blood-clotting factor, cancer-fighting proteins • Also gene therapy – the process of changing a gene to treat a medical disease or disorder • Absent or faulty gene replaced with a normal, working gene

39. Treating Disease • Very risky • Need a more reliable way to insert working genes • Make sure it’s not harmful

40. Genetic Testing • Hundreds of diseases/disorders can be tested for • Some use labeled DNA probes that can detect disease-causing alleles • Some search for changes in cutting sequences • Some use PCR to detect differences in length between normal and abnormal alleles

41. Examining Active Genes • Not every gene is active in ever cell all the time • Understand how cells function by studying active genes using DNA microarray technology - measures level of activity of genes

42. DNA Microarray • Glass slide or silicon chip to which spots of single-stranded DNA are attached – each spot with a different DNA fragment • Colored tags label source of DNA

44. DNA Microarray • Red spots = more cancer mRNA • Green spots = more normal mRNA • Yellow spots = both

45. Personal Identification • No 2 individuals are genetically identical (except identical twins) • Regions of chromosomes contain repeated sequences that do not code for proteins that differ from person to person

46. Personal Identification • DNA fingerprinting analyzes sections of DNA that have little/no function but that vary widely from one individual to another • Use REs to cut DNA into fragments, electrophoresis to separate fragments

47. Personal Identification • DNA probe detects fragments with highly variable regions • If enough probe/enzyme combos are used, resulting banding pattern can be used to distinguish a person • DNA from any tissue can be used

48. Forensic Science • Forensics = study of crime scene evidence • Uses DNA fingerprinting to solve crimes, overturn convictions • Wildlife conservation

49. Establishing Relationships • When genes are passed parent to child, the markers used in DNA fingerprinting are scrambled • Y chromosome, however, passed directly from father to son with few changes – paternity tests • Pieces of mitochondrial DNA (mtDNA) also passed from mother to child directly – 2 people with the same mtDNA share a common maternal ancestor