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Ch 15 Advances in Molecular Genetics

Ch 15 Advances in Molecular Genetics

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Ch 15 Advances in Molecular Genetics

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  1. Ch 15Advances in Molecular Genetics 2 5 New techniques mean new questions we can ask about REALLY small things… like Genes 6 1 4

  2. 15.1 The Genome Projects8 Researchers try to catalog an organism’s genes and find out what the genes do… Human Genome Project (HGP) • Human Genome = 3 billion base pairs • ~100,000 genes • Coordinated by the Human Genome Organization • Sponsored by governments and companies Machines can sequence 100s of base pairs per hour!

  3. Other Organisms Sequenced E. coli, 3515x – one of the first…9 S. cerevisiae, 3085x – first eukaryote9See p. 394 to see a simplified gene map C. elegans, nematode, first multicellular organism10

  4. 15.3 Genetic Engineering Changing genes at the sequence level or moving them from one organism to another Recombinant DNA: DNA from 2 or more sources combined together. Transformation: Moving DNA from a source into an organism’s DNA 1. Identify and isolate gene of interest 2. Find a way to carry the DNA into the host genome (using a Vector) 3. Identify cells that have taken up the gene

  5. Tools of the Trade 1. Restriction Enzymes: specialized “molecular scissors” which cut DNA at known, specific sequences Originally found in bacteria to cut up and destroy (restrict) viral DNA 2.DNA Ligase: Enzyme which covalently bonds DNA (remember Okazaki fragments?) 3. Vectors: A way to get DNA into other cells – Eg. Plasmids or viruses 4. Resistance Genes: Allow bacteria to survive antibiotics. Usually placed on the plasmid.

  6. Restriction Enzymes (Endonucleases)22 20-02-RestrictionEnzymes.swf

  7. DNA isolated from two sources and cut by samerestriction enzyme Plasmid(vector) Gene of interest(could besynthesized orobtained fromlibrary) Recombinant DNA Transgenic organisms Useful products Transformation with Plasmids Creating recombinant plasmid DNA Competent cells can take up the plasmid vector and your gene. 12_06AN Transformation.MOV 22

  8. Some Uses of Recombinant DNA15

  9. PCR – Polymerase Chain Reaction3 Also see P. 401 – This is all based on alternating high temperature cycles with cooler temperature cycles

  10. Gel Electrophoresis Sample DNA Gel21 Molecules sorted by: - Size - Charge Gel matrix 19

  11. RFLP Analysis14 See P. 402 Restriction Fragment Length Polymorphism a. Differences in DNA sequence yield different length DNA fragments when the samples are cut with the same restriction enzyme. b. You can detect these differences using gel electrophoresis.

  12. Using RFLPs to identify evidence Crime scene Suspect 1 Suspect 2 Blood on defendant’sclothes Defendant’sblood Victim’sblood DNA DNA DNA Polymerase chainreaction (PCR)amplifies DNA samples Longerfragments Gel Shorterfragments DNA Fingerprinting

  13. 15.4 DNA Mutations and Repair15 See P. 406 Is a mutation always bad? Frameshift Mutation Point Mutation/Substitution

  14. Sickle Cell – A Point Mutation22

  15. Translocation Often cause problems because genes are disrupted or changed during the exchange of DNA – may cause diseases like cancer. It is basically crossing over between non-homologous chromosomes!

  16. Chromosomal Inversion20

  17. Somatic Cell Mutations18 Occur in the body cells, not gametes • Can cause the death of the cell • Can cause cancer • Gene Amplification: a natural part of some cells’ development. • Some cells are specialized for specific protein synthesis • Extra copies of these specific genes are created • May be inserted in chromosomes or float in cytoplasm Eg. rRNA genes

  18. Germ-Line Therapy: changes genes in individual’s gametes Somatic Cell Therapy:changes DNA in body cells Can use viruses or vesicles as vectors Insertion into the genome is at random locations Can disrupt other genes 15.5 Genetic Disorders and Gene Therapy15 15

  19. 7 15.6 Ethical, Legal, and Social Issues Identifying variation in genes is getting easier and easier… Raising new questions… • How much information should governments, insurers, or employers have about your genes? • Should discrimination on the basis of genes be allowed? • When gene therapy works well,we’ll be able to change our own genes. When should we? • Is the information worth theprice?

  20. Sources Cited 1. sequencing/ 2. naf/Sequencing.html 3. 4. ~reddy/labtour2.htm 5. 6. ~72332/ 7. neweconomy/13.html 8. sheets/36.html 9. with permission 10. Celegans/Images/fig1.htm 11. 12. 13. nats/day15.htm 14. 3250_Recombinant_DNA.htm 15. BioCD. From Biology, Fifth Edition. Campbell, Reece, Mitchell. Addison, Wesley, Longman. 1999. 16. hgp/tools.htm 17. 18. advbio1protsyn.html 19. 20. genetics/variat2.htm 21. 22. Bioshow: for Biology: Concepts and Connections, Second Edition. Campbell, Mitchell, and Reece