Chapter 15

1. Chapter 15 Genetic Engineering

2. Chapter MysteryA case of mistaken identity • Page 417 • Hypothesis: How did the police know they had the wrong suspect?

3. Section 15.1Selective Breeding • Objectives: • What is selective breeding used for ? • How do people increase genetic variation? • Define: • Selective breeding • Hybridization • Inbreeding • biotechnology

4. I. Selective Breeding • Dogs = Chihuahua  Great Dane • Humans bred dogs for 1000s of years looking to produce better hunters, retrievers, companions • Selective breeding – allowing only those animals with wanted characteristics to produce the next generation • Humans use selective breeding, which takes advantage of naturally occurring genetic variation, to pass wanted traits on to the next generation of organisms • Produced new varieties of cultivated plants and all domestic animals (horses, cats, cows) by selectively breeding for particular traits • Native Americans selectively bred teosinte (wild grass) to produce corn = more nutritious and productive

5. A. Hybridization • Luther Burbank (1849 – 1926) – developed >800 varieties of plants • Hybridization – crossing dissimilar individuals to bring together best of both organisms • Hybrids – individuals produced by crosses • Often hardier than either of parents • Burbank’s crosses combined disease resistance of one plant w/ food-producing capacity of another • Results in new line of plants that had traits farmers needed to increase food production

6. B. Inbreeding • Inbreeding – continued breeding of individuals with similar characteristics • Used to maintain desirable characteristics in a line of organisms • Helps ensure that characteristics that make each breed unique are preserved • Can be risky • Most members of a breed = genetically similar • Increases chance that a cross b/w 2 individuals will bring together 2 recessive alleles for genetic defect

7. II. Increasing Variation • Breeders can increase the genetic variation in a population by introducing mutations, which are the ultimate source of biological diversity • Biotechnology – application of a technological process, invention, or method • Used when manipulate genetic makeup of an organism • Selective breeding = one form (important in agriculture and medicine)

8. A. Bacterial Mutations • Mutations – heritable changes in DNA • Occur spontaneously • Can be increased by breeders by using radiation or chemicals • Many harmful to organism • With luck and perseverance  breeders can produce a few mutants w/ useful characteristics not found in original population • Useful in bacteria • Small • Millions can be treated w/ radiation/chemicals at same time = increases chance of producing a useful mutant • Scientists have produced 100s of useful bacteria • Some consume oil (oil spills) • Working on bacteria that can clean up radioactive substances and metal pollution in environment

9. B. Polyploid Plants • Drugs that prevent separation of chromosomes during meiosis = useful in plant breeding • Produce cells that have many times normal number of chromosomes • Plants grown from these cells = polyploid b/c they have many sets of chromosomes • Polyploidy – usually fatal in animals; plants much better at tolerating extra sets of chromosomes • Can quickly produce new species of plants: larger and stronger than diploid relatives • Bananas, citrus fruits

10. Section 15.2Recombinant DNA • Objectives: • How do scientists copy the DNA of living organism? • How is recombinant DNA used? • How can genes from one organism be inserted into another organism? • Define: • Polymerase chain reaction • Recombinant DNA • Plasmid • Genetic marker • Transgenic • Clone

11. I. Copying DNA • In the past – mutations unpredictable • Today – genetic engineers can transfer certain genes at will from one organism to another = new living things • DNA extracted from cells  cut into fragments  separated according to size  find DNA of single gene among 3 million fragments!!!!

12. Mystery Clue • Page 421… • How could restriction enzymes be used to analyze the DNA evidence found on the suspect?

13. A. Finding Genes • 1987 – Douglas Prasher – jellyfish • wanted to find gene that codes for green fluorescent protein • GFP – absorbs energy from light & makes jellyfish parts glow • Wanted to link GFP to when a protein was being made in a cell • To find the gene using mRNA and radioactive probes to bind to complementary base sequences

14. B. Polymerase Reaction Chain • Heat piece of DNA  separates strands • As DNA cools, primer binds to single strands • DNA polymerase starts copying region b/w primers • Copies serve as templates to make more copies

15. II. Changing DNA • Wondered how to change DNA of living cell • Griffith answered  transformation: cell takes DNA from outside cell, added DNA becomes component of cell’s own genome • Heat-killed bacteria contained DNA fragments • When mixed w/ live bacteria  some took up fragments  transformed bacteria (changed characteristics

16. A. Combining DNA Fragments • Today – can build custom DNA molecules with genes you like & insert them into living cells • Recombinant DNA technology – joining together DNA from 2 or more sources • Makes it possible to change the genetic composition of living organisms • Can investigate the structure and function of genes

17. B. Plasmids and Genetic Markers • Scientists join recombinant DNA to another piece of DNA containing a replication “start” signal  whenever cell copies its own DNA, it copies recombinant DNA too • Plasmid – small circular DNA molecule • Join DNA to plasmid  use recombinant plasmid to transform bacteria  results in replication of newly added DNA w/ rest of cell’s genome • Genetic marker – gene that makes it possible to distinguish bacteria that carry the plasmid from those that don’t • Used to locate transformed cells

18. III. Transgenic Organisms • Transgenic – contain genes from other species • Transgenic organisms can be produced by the insertion of recombinant DNA into the genome of a host organism • 1980’s – perfected using mice • Now – plants, animals, microorganisms • Contributes to understanding gene regulation and expression

19. A. Transgenic Plants

20. B. Transgenic Animals

21. C. Cloning • Clone – member of a population of genetically identical cells produced from a single cell • Use single cell from adult organism to grow an entirely new individual that is genetically identical to organism from which cell was taken • 1952 – 1st clone of animals – amphibian tadpoles • 1997 – Ian Wilmut – cloned sheep “Dolly” • Since = cloned cows, pigs, mice, cats

22. Section 15.3Applications of Genetic Engineering • Objectives: • How can genetic engineering benefit agriculture and industry? • How can recombinant-DNA technology improve human health? • How is DNA used to identify individuals? • Define: • Gene therapy • DNA microarray • DNA fingerprinting • forensics

23. I. Agriculture and Industry • Everything we eat and much of what we wear come from living organisms • Use genetic engineering to try to improve products from plants and animals • Ideally, genetic modification could lead to better, less expensive, and more nutritious food as well as less-harmful manufacturing processes.

24. A. GM Crops • Introduced 1996 • 2007 – GM crops = 92% soybeans; 86% cotton; 80% corn grown in US • Use bacterial genes that produce protein (Bt toxin) • Harmless to humans • Enzyme in insects converts Bt toxin into a form that kills the insect • No pesticides needed & produce higher yield of crops • Resistance to herbicides (chemicals that destroy weeds) • Resistance to viral infections • Produce foods resistant to rot and spoilage (soon) • Produce plastics for manufacturing industry (soon)

25. B. GM Animals • Food supply • 30% milk from cows injected w/ hormones made by recombinant-DNA techniques to increase milk production • Pigs – produce more lean meat or high levels of healthy omega-3 acids • Salmon – growth hormone = grow more quickly (grown in captivity) • Spider genes into goats = manufacture silk w/ milk  extracted & woven into thread = light, tough, flexible material (military uniforms, medical sutures, tennis racket strings) • Human genes + goat milk = antibacterial goat milk • Hope to clone transgenic animals • Increase food supply • Save endangered species • 2008 – US gov’t approved sale of meat and milk from cloned animals

26. II. Health and Medicine • Biotechnology = part of medicine • Early physicians – extracted substances from plants and animals to cure patients • 20th century – vaccination saved countless lives • Today – recombinant-DNA technology source of some of most important advances in prevention and treatment of disease

27. A. Preventing Disease • Golden rice – incr. provitamin A + beta-carotene • Hope to help prevent health problems (infant blindness) • Transgenic plants/animals to make human antibodies • Future transgenic animals may supply us w/ human proteins  used in disease prevention • Already produced in milk of some transgenic sheep and pigs

28. B. Medical Research • Transgenic animals – used as test subjects • Simulate human diseases caused by defective genes • Use models based on simulations to follow onset and progression of diseases & test new drugs that may treat disease • Ex: Alzheimer’s & arthritis

29. C. Treating Disease • Recombinant-DNA technology  make important proteins that could prolong or save human lives • Human growth hormone – used to treat pituitary dwarfism  now widely available b/c mass produced in recombinant bacteria • Insulin – treat diabetes • Blood-clotting factors – hemophilia • Interleukin-2 & interferon – cancer (future)

30. Gene therapy – process of changing a gene to treat a medical disease/disorder • Absent or faulty gene is replaced by a normal, working gene • Allows body to make the protein/enzyme needed  eliminates cause of disorder • Human Genome Project • How it works: • Engineer virus that cannot reproduce or cause harmful effects • Put DNA w/ therapeutic gene into modified virus • Infect patient’s cells w/ virus • In theory: virus will insert healthy gene into target cell and correct defect • Challenge: deliver gene that works correctly over long term • High risk & experimental procedure • To become accepted treatment  need more reliable ways to insert working genes and ensure DNA used does no harm

31. D. Genetic Testing • Genetic tests – use specific DNA sequences that detect complementary base sequences found in disease-causing alleles • Other tests – search for changes in cutting sites of restriction enzymes • Some – use tests to detect differences b/w length of normal and abnormal alleles • Available for diagnosing hundreds of disorders

32. E. Examining Active Genes • All cells in human body contain identical genetic material • Same genes not active in every cell • DNA microarray technology – used to study 100s/1000s of genes at once to understand levels of gene activity

33. III. Personal Identification • Complexity of human genome = no individual is exactly like any other genetically • DNA fingerprinting analyzes sections of DNA that may have little or no function but that vary widely from one individual to another • DNA samples from blood, sperm, tissue, hair w/ root

34. A. Forensic Science • Used since 1980s • Precise & reliable • Forensics – scientific study of crime scene evidence • DNA fingerprinting – solve crimes, convict criminals, overturn wrongful convictions • Wildlife conservation – identify herds from which black-market ivory was taken (elephants in Africa)

35. B. Establishing Relationships • DNA fingerprinting  disputed paternity: alleles in child not carried by mother must come from father • Y chromosome – never crosses over=few changes (father to child) • miDNA (mitochondrial)- small so few changes (mother to child)

36. Mystery Clue • Page 434… • What kind of evidence do you think investigators collected at the crime scene? • What kinds of tests would they have to run on this evidence? • What would the tests have to show before the suspect was released?

37. Section 15.4 Ethics and Impacts of Biotechnology • Objectives: • What privacy issues does biotechnology raise? • Are GM foods safe? • Should genetic modifications to humans and other organisms be closely regulated? • Assignment  2-column Chart & Essay: • Write both viewpoints for each issue in this section to help you create a view point for each question above • Write your opinion answer for each question above… use support from the reading that is now in your chart

38. I. Profits and Privacy

39. II. Safety of Transgenics

40. Mystery Clue • Page 437… • What privacy considerations, if any, should investigators have taken into account when obtaining the DNA evidence?

41. III. Ethics of the New Biology

42. Solve the Mystery • Page 443… • How did the investigators determine that the person they took into custody was not guilty of this crime? • Did the DNA evidence from the bloodstains come from the red blood cells, white blood cells, or both? EXPLAIN. • What if the initial suspect was related to the victim? Would that have changed the result? Why or why not? • What might have happened if this crime were committed before DNA fingerprinting was discovered? Describe the series of events that might have taken place after police took in the first suspect.