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Chapter 13

Chapter 13. GENETIC ENGINEERING. Genetic variation. How are a great dane and a chihuahua similar? All dogs are the same species LOTS of genetic variation! How did this happen? We did it!. Selective breeding.

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Chapter 13

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  1. Chapter 13 GENETIC ENGINEERING

  2. Genetic variation • How are a great dane and a chihuahua similar? • All dogs are the same species • LOTS of genetic variation! • How did this happen? • We did it!

  3. Selective breeding • Selective breeding: a method of breeding organisms with desired characteristics to provide the next generation with that trait • Takes advantage of natural genetic variation • Luther Burbank- selectively bred disease-resistant potatoes

  4. hybridization • Hybridization: breeding technique that crosses dissimilar individuals to bring together the best traits of each • Hybrid: offspring of hybridization • Ex: crossing a large sized potato with a potato that is disease-resistant Or a hybrid car… …or a mule!

  5. inbreeding • Inbreeding: continued breeding of individuals with similar (desired) characteristics • You get the desired traits but… • Increased chance of other defects (ex: 2 recessive alleles)

  6. Genetic variation • Increased genetic variation = possibility of breeding mutants (but this is a good thing) • Remember the 4 criteria for a gene? • Mutations are the BIGGEST source of genetic variation • Whether good or bad, mutations are new to a population and increase diversity

  7. Producing new kinds of organisms • Treat with radiation or chemicals to mutate • Bacteria • small and multiply quick/easy to pass along mutation • Ex: bacteria that digest oil (used in oil spills) • Plants • Chemicals prevent chromosome separation in meiosis • End up with extra sets of chromosomes (polyploids)

  8. 13-2 Manipulating DNA • What does it mean to “manipulate” DNA? • To change it! • Selective breeding and inbreeding use natural genetic variation…but its unpredictable! • Now, we can “rewrite” the code

  9. How do we change dna? • Must have knowledge of structure and chemical properties • New technology: • 1. extraction techniques • 2. cut into smaller pieces • 3. identify base sequences • 4. make unlimited copies

  10. 1. Dna extraction • Like in our strawberry lab! • Open up the cell and nucleus • Separate DNA from everything else

  11. 2. Cutting dna… • Restriction enzymes: enzyme that cuts DNA at a specific sequence of nucleotides • Very specific • Recombinant DNA: DNA produced by combining DNA from different sources • Ex: human insulin gene and pig DNA- have pigs produce insulin

  12. …and separating DNA • Gel electrophoresis: procedure used to separate + analyze DNA fragments • Place DNA (- charge) at one end of a gel and apply + charge to the other • Fragments move across gel- smaller move faster/further • Used to compare/contrast/identify particular genes

  13. 3. Identifying base sequences • Used to study specific genes, compare, discover functions, etc. • To “read” the sequence = determine the order of bases • Sequencing: • Start with unknown strand + DNA polymerase +nucleotide bases = complimentary strand is made • Bases are dyed to identify them • Now, everything is automated

  14. 4. Making copies • Polymerase chain reaction (PCR): technology that allows scientists to make many copies of a gene • How it works: • Heat DNA- strands separate • Cool and add primers- short pieces of DNA that tell DNA polymerase to start working • Add free nucleotide bases + DNA polymerase • Makes a new stand- like artificial DNA replication!

  15. 13-3 cell transformation • What is transformation? • Taking in DNA from outside the cell- this “external” DNA then becomes part of the new cell’s DNA • DNA MUST be integrated into a chromosome! • Recombinant DNA!

  16. Transforming bacteria • Plasmid: small circular DNA molecule • Why plasmids? • Replicate easily so foreign DNA will then be replicated • Genetic marker: a gene that distinguishes bacteria with foreign DNA plasmid from ”regular” bacteria • Antibiotics resistant genes used alot

  17. Transforming plant cells • Use bacterium that inserts a plasmid with manipulated foreign DNA into plant cells • Can also: • Take up DNA when cell wall is removed • Inject DNA directly into plant cells • Either way, DNA MUST be integrated into the chromosome

  18. Transforming animal cells • Cells are large enough for direct injection of DNA • Enzymes used to cut and insert DNA into chromosome • May also use genetic markers • Gene replacement- replace one gene with another

  19. 13-4 Applications of ge • GE = biotechnology • Can we combine plant and animal genes? • YES! • Luciferase enzyme (firefly glow) + tobacco plant = a glowing plant

  20. Transgenic organisms • Transgenic organism: an organism that contains genes from a different organism • Gene from one inserted into the cell of another • These transformed cells = a new organism!

  21. Transgenic microorganisms • Insert human gene for proteins into bacteria • Bacteria used to “harvest” human proteins • Ex: insulin, growth factors, clotting factors

  22. Transgenic plants • Examples: • Plants with natural insecticides • Plants that will resist weed-killing chemicals • Rice with added vitamin A

  23. Transgenic animals • For research: • mice with human immune systems • For food: • Livestock with added growth hormone- grow faster/leaner • Chicken that is resistant to food poisoning bacteria • Milk that produces human proteins in it

  24. cloning • Clone: a member of a population of genetically identical cells produced from a single cell • Single-celled bacteria= easy to clone • Multicellular organism= more difficult • “Dolly” the sheep- cloned by Ian Wilmut in 1997

  25. How did he do it? • De-nucleate an egg cell • Donor nucleus fuses to the de-nucleated cell • Fused using an electric shock • Cell will begin to divide- form an embryo • Embryo is placed in foster mom’s uterus • Development and birth happen as normally does

  26. cloning

  27. Cloning Pros and cons • Pros • Ability to reproduce transgenic animals • Ability to reproduce endangered species • Cons • Genetic defects • Unknown side effects • What else?

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