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13 Changing the Living World (In a nutshell) How can genetics be used to change organisms? Slide 1 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Selective Breeding Selective Breeding Selective breeding allows only those organisms with desired characteristics to produce the next generation. Nearly all domestic animals and most crop plants have been produced by selective breeding. Slide 2 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Selective Breeding Humans use selective breeding to pass desired traits on to the next generation of organisms. Slide 3 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Selective Breeding Hybridization Hybridization is the crossing of dissimilar individuals to bring together the best of both organisms. Hybrids, the individuals produced by such crosses, are often hardier than either of the parents. Slide 4 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Selective Breeding Inbreeding Inbreeding is the continued breeding of individuals with similar characteristics. Inbreeding helps to ensure that the characteristics that make each breed unique will be preserved. Serious genetic problems can result from excessive inbreeding. Slide 5 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Increasing Variation Breeders increase the genetic variation in a population by inducing mutations. Slide 6 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Increasing Variation Mutations occur spontaneously, but breeders can increase the mutation rate by using radiation and chemicals. Breeders can often produce a few mutants with desirable characteristics that are not found in the original population. Slide 7 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Increasing Variation Producing New Kinds of Bacteria Introducing mutations has allowed scientists to develop hundreds of useful bacterial strains, including bacteria that can clean up oil spills. Slide 8 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Increasing Variation Producing New Kinds of Plants Mutations in some plant cells produce cells that have double or triple the normal number of chromosomes. This condition, known as polyploidy, produces new species of plants that are often larger and stronger than their diploid relatives. Polyploidy in animals is usually fatal. Slide 9 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World The Tools of Molecular Biology The Tools of Molecular Biology How do scientists make changes to DNA? Slide 10 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World The Tools of Molecular Biology Scientists use different techniques to: extract DNA from cells cut DNA into smaller pieces identify the sequence of bases in a DNA molecule make unlimited copies of DNA In genetic engineering, biologists make changes in the DNA code of a living organism. Slide 11 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World The Tools of Molecular Biology DNA Extraction DNA can be extracted from most cells by a simple chemical procedure. The cells are opened and the DNA is separated from the other cell parts. Cutting DNA Most DNA molecules are too large to be analyzed, so biologists cut them into smaller fragments using restriction enzymes. Slide 12 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World The Tools of Molecular Biology Each restriction enzyme cuts DNA at a specific sequence of nucleotides. Recognition sequences DNA sequence Restriction enzyme EcoR I cuts the DNA into fragments Sticky end Slide 13 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World The Tools of Molecular Biology Separating DNA In gel electrophoresis, DNA fragments are placed at one end of a porous gel, and an electric voltage is applied to the gel. Slide 14 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World The Tools of Molecular Biology Power source DNA plus restriction enzyme Longer fragments Mixture of DNA fragments Gel Gel Electrophoresis Copyright Pearson Prentice Hall Shorter fragments Slide 15 of 18 End Show 13-1 Changing the Living World First, restriction enzymes cut DNA into fragments. The Tools of Molecular Biology DNA plus restriction enzyme The DNA fragments are poured into wells Mixture of DNA on a gel. fragments Gel Electrophoresis Copyright Pearson Prentice Hall Gel Slide 16 of 18 End Show 13-1 Changing the Living World An electric voltage is applied to the gel. The smaller the DNA fragment, the faster and farther it will move across the gel. The Tools of Molecular Biology Power source Slide 17 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World The Tools of Molecular Biology Power source Longer fragments Shorter fragments Gel Electrophoresis Slide 18 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Using the DNA Sequence Making Copies Polymerase chain reaction (PCR) is a technique that allows biologists to make copies of genes. Small amounts of DNA can be multiplied making it easier to analyze. Made possible by an enzyme found in a bacterium living in hot springs in Yellow Stone National Park. Slide 19 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Using the DNA Sequence Polymerase Chain Reaction (PCR) DNA heated to separate strands DNA polymerase adds complementary strand DNA fragment to be copied PCR cycles 1 DNA copies 1 2 2 3 4 4 8 5 etc. 16 etc. Slide 20 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Transgenic Organisms Transgenic Organisms An organism described as transgenic, contains genes from other species. Genetic engineering has spurred the growth of biotechnology. How do we make them? (specifically bacteria) Slide 21 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Transforming Bacteria Foreign DNA is first joined to a small, circular DNA molecule known as a plasmid. Plasmids are found naturally in some bacteria and have been very useful for DNA transfer. The plasmid has a genetic marker—a gene that makes it possible to distinguish bacteria that carry the plasmid (and the foreign DNA) from those that don't. Slide 22 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Slide 23 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Transgenic Organisms Transgenic Microorganisms Transgenic bacteria produce important substances useful for health and industry. Transgenic bacteria have been used to produce: • insulin • growth hormone • clotting factor Slide 24 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Cloning Dolly and Bonnie Cloning A clone is a member of a population of genetically identical cells produced from a single cell. In 1997, Ian Wilmut cloned a sheep called Dolly. Slide 25 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Cloning Cloning Dolly Donor Nucleus Fused cell Egg Cell Embryo Cloned Lamb Foster Mother Copyright Pearson Prentice Hall Slide 26 of 18 End Show 13-1 Changing the Living World Cloning Cloning Dolly Slide 27 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Cloning Cloning Dolly Slide 28 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Cloning Cloning Dolly Slide 29 of 18 Copyright Pearson Prentice Hall End Show 13-1 Changing the Living World Cloning Researchers hope cloning will enable them to make copies of transgenic animals and help save endangered species. Studies suggest that cloned animals may suffer from a number of genetic defects and health problems. Slide 30 of 18 Copyright Pearson Prentice Hall End Show