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Download 12.11 Restriction fragment analysis is a powerful method that
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12.10 Gel electrophoresis sorts DNA molecules by size • Restriction fragments of DNA can be sorted by size Mixture of DNA molecules of different sizes Longer molecules Power source Gel Shorter molecules Glass plates Completed gel Figure 12.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 12.11 Restriction fragment analysis is a powerful method that detects differences in DNA sequences • Scientists can compare DNA sequences of different individuals based on the size of the fragments Allele 1 Allele 2 w Cut z x Cut y Figure 12.11A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cut y DNA from chromosomes 1 2 Longer fragments Shorter fragments Figure 12.11B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Radioactive probes are also used to make comparisons 1 Restriction fragment preparation Restriction fragments 2 Gel electrophoresis 3 Blotting 4 Radioactive probe Filter paper Radioactive, singlestranded DNA (probe) Probe 5 Detection of radioactivity (autoradiography) Film Figure 12.11C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 12.12 The PCR method is used to amplify DNA sequences • The polymerase chain reaction (PCR) can quickly clone a small sample of DNA in a test tube Initial DNA segment 1 2 4 Number of DNA molecules Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 8 Figure 12.12 OTHER APPLICATIONS OF DNA TECHNOLOGY 12.15 Connection: DNA technology is used in courts of law • DNA fingerprinting can help solve crimes Defendant’s blood Blood from defendant’s clothes Victim’s blood Figure 12.15A, B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 12.16 Connection: Recombinant cells and organisms can mass-produce gene products • Recombinant cells and organisms are used to manufacture useful proteins Table 12.16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • These sheep carry a gene for a human blood protein that is a potential treatment for cystic fibrosis Figure 12.16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 12.17 Connection: DNA technology is changing the pharmaceutical industry and medicine • Hormones, cancer-fighting drugs, and new vaccines are being produced using DNA technology – This lab equipment is used to produce a vaccine against hepatitis B Figure 12.17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 12.18 Connection: Genetically modified organisms are transforming agriculture • New genetic varieties of animals and plants are being produced – A plant with a new trait can be created using the Ti plasmid Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Agrobacterium tumefaciens DNA containing gene for desired trait 1 Ti plasmid T DNA Insertion of gene into plasmid using restriction enzyme and DNA ligase Plant cell 2 Recombinant Ti plasmid Restriction site Introduction into plant cells in culture 3 Regeneration of plant T DNA carrying new gene within plant chromosome Plant with new trait Figure 12.18A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • “Golden rice” has been genetically modified to contain beta-carotene – This rice could help prevent vitamin A deficiency Figure 12.18B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 12.19 Connection: Gene therapy may someday help treat a variety of diseases • Techniques for manipulating DNA have potential for treating disease by altering an afflicted individual’s genes Cloned gene (normal allele) 1 Insert normal gene into virus Viral nucleic acid Retrovirus 2 Infect bone marrow cell with virus – Progress is slow, however 3 Viral DNA inserts into chromosome – There are also ethical questions related to gene therapy Bone marrow cell from patient Bone marrow 4 Inject cells Figure 12.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings into patient RISKS AND ETHICAL QUESTIONS 12.20 Connection: Could GM organisms harm human health or the environment? • Genetic engineering involves some risks – Possible ecological damage from pollen transfer between GM and wild crops – Pollen from a transgenic variety of corn that contains a pesticide may stunt or kill monarch caterpillars Figure 12.20A, B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 12.21 Connection: DNA technology raises important ethical questions • Our new genetic knowledge will affect our lives in many ways • The deciphering of the human genome, in particular, raises profound ethical issues – Many scientists have counseled that we must use the information wisely Figure 12.21A-C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings