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A Lot More Advanced Biotechnology Tools DNA Sequencing
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–dideoxynucleotides ddATP, ddGTP, ddTTP, ddCTP missing O for bonding of next nucleotide terminates the growing chain DNA Sequencing
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Sanger method –synthesize complementary DNA strand in vitro –in each tube: “normal” N-bases dideoxy N-bases –ddA, ddC, ddG, ddT DNA polymerase primer buffers & salt 2 1 3 4 2
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Reading the sequence Load gel with sequences from ddA, ddT, ddC, ddG in separate lanes –read lanes manually & carefully –polyacrylamide gel
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Fred Sanger 1978 | 1980 This was his 2nd Nobel Prize!! –1st was in 1958 for the structure of insulin
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The Sanger Method: DNAi video tutorial
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Advancements in sequencing Fluorescent tagging –no more radioactivity –all 4 bases in 1 lane each base a different color Automated reading
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Applied Biosystems, Inc (ABI) built an industry on these machines More Advancements in sequencing Capillary tube electrophoresis no more pouring gels higher capacity & faster
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PUBLIC Joint Genome Institute (DOE) MIT Washington University of St. Louis Baylor College of Medicine Sanger Center (UK) PRIVATE Celera Genomics Big labs! economy of scale
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Automated Sequencing machines Really BIG labs!
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Human Genome Project U.S government project –begun in 1990 estimated to be a 15 year project –DOE & NIH initiated by Jim Watson led by Francis Collins –goal was to sequence entire human genome 3 billion base pairs Celera Genomics –Craig Venter challenged gov’t –would do it faster, cheaper –private company
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Different approaches 3. Assemble DNA sequence using overlapping sequences. “map-based method” gov’t method “shotgun method” Craig Venter’s method 1. Cut DNA entire chromosome into small fragments and clone. 2. Sequence each segment & arrange based on overlapping nucleotide sequences. 1.Cut DNA segment into fragments, arrange based on overlapping nucleotide sequences, and clone fragments. 2. Cut and clone into smaller fragments.
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Shotgun!
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Human Genome Project On June 26, 2001, HGP published the “working draft” of the DNA sequence of the human genome (4 years ahead of schedule). Historic Event! –blueprint of a human –the potential to change science & medicine
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Sequence of 46 Human Chromosomes 3 billion base pairs 3G of data
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Things Are Strange In Here:
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Raw genome data
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NCBI GenBank Database of genetic sequences gathered from research Publicly available on Web!
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Maps of human genes… Where the genes are… –mapping genes & their mutant alleles
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Defining a gene… “Defining a gene is problematic because… one gene can code for several protein products, some genes code only for RNA, two genes can overlap, and there are many other complications.” – Elizabeth Pennisi, Science 2003 gene polypeptide 1 polypeptide 2 polypeptide 3 protein gene RNA
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Types of DNA sequences in the human genome Exons (regions of genes coding for protein, rRNA, tRNA) (1.5%) Repetitive DNA that includes transposable elements and related sequences (44%) Introns and regulatory sequences (24%) Unique noncoding DNA (15%) Repetitive DNA unrelated to transposable elements (about 15%) Alu elements (10%) Simple sequence DNA (3%) Large-segment duplications (5–6%)
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And we didn’t stop there…
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Genome Sizes and Estimated Numbers of Genes*
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What have we found? When you go looking…
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…you will certainly find something!
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Sing A Silly Song Extolling Automation!
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Ethical Questions…
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1. You have a familiar history of a terminal genetic disease. A genetic test exists for the disease. Would you take the test to see if you will have the disease?
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2. As a condition of your continued employment, your boss wants you to have a genetic screening test and the results sent to the company. Will you get the test?
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3. You and your spouse have decided to have a child. You have the resources to pre-determine your child’s gender. Would you do this? 4. What about your child’s intelligence?
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5. You discover your favorite food contains genetically modified ingredients. Will you continue to eat the food?
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6. As part of a routine medical procedure, your doctor discovers that you have a rare, beneficial variant of a protein that protects you from heart disease. Should your doctor be able to patent the protein? 7. Should you be entitled to any money from the patent?
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