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Chapter 13 – Recombinant DNA and Genetic Engineering

Chapter 13 – Recombinant DNA and Genetic Engineering. College Prep Biology Mr. Martino. Introduction. Gene Therapy: transfer of one or more modified genes into an individual’s cells Correct genetic defect Boost immune system

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Chapter 13 – Recombinant DNA and Genetic Engineering

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  1. Chapter 13 – Recombinant DNA and Genetic Engineering College Prep Biology Mr. Martino

  2. Introduction • Gene Therapy: transfer of one or more modified genes into an individual’s cells • Correct genetic defect • Boost immune system • Recombinant DNA Technology: science of cutting and recombining DNA from different species • Genes are then placed into bacterial, yeast or mammalian cells and replicated • Genetic Engineering: genes are isolated, modified, and inserted back into a cell • also called biotechnology

  3. 15.1 Making Recombinant DNA • Restriction enzyme: enzyme that chops up DNA at a specific sequence • Bacterial • Viral defense mechanism • May cut a DNA strand a few times • Helpful in studying DNA • Produces “sticky ends” which may pair with other DNA • Genome: all the DNA in a haploid number of chromosomes for each species

  4. Plasmids: small circle of DNA • In bacterial cells • Insert foreign DNA (gene) into and put back in bacteria – reproduces naturally making a DNA clone • Cloning vector: plasmid used to accept foreign DNA and replicate it • Reverse transcriptase: enzyme from RNA viruses that perform transcription in reverse (RNA to DNA) • cDNA: (copied DNA) mature mRNA transcript that has already been spliced • Bacteria cannot remove introns and splice exons • Reverse transcriptase makes DNA from mRNA to insert into plasmid

  5. 15.2 PCR – Polymerase Chain Reaction • PCR: a fast method of amplifying (making lots of copies) DNA • DNA isolated, mixed with DNA polymerase, nucleotides, and some other good stuff • Produces 2 daughters • Daughters replicate, etc. • 1 DNA molecule generates 100 billion in a few hours • Used in evolution research, analyze DNA from fossils, analyze embryos, court cases

  6. 15.3 DNA Fingerprints • No two people have exactly identical DNA • Except identical twins • DNA Fingerprint: unique set of DNA fragments • Used to determine paternity, solve crimes, etc. • 99.9% all human DNA is identical • Focus on highly variable areas of tandem repeats • Mutations occur within families and are more common in these areas

  7. Gel electrophoresis: uses an electric current to force DNA fragments through a gel • DNA is negative • Size of fragment determines how far it migrates • The fewer tandem repeats the farther it travels • Differences in homologous DNA sequences resulting in fragments of different lengths are restriction fragment length polymorphisms (RFLP’s)

  8. 15.4 DNA Sequencing • 1995 – entire DNA sequence for a bacterium was determined • 4/25/03 – Human genome completed • Several bacteria, yeast, Drosophila,C. elegans - worm, Arabidopsis - weed, Mickey…a mouse, just completed 3/31/04 – a rat) • Used a sequencing machine

  9. 15.5 Isolating Genes • Genomic Library: set of DNA fragments from an organism’s genome • Complementary RNA sequence can be synthesized with a radioactive isotope tag called a probe • Used to find a specific gene • Tags the gene whenever encountered • Gene may then be isolated

  10. 15.6 Using the Technology • True human insulin is now manufactured • Also somatotropin (growth hormone), blood-clotting factors, hemoglobin, interferons (cancer research), and various other drugs and vaccines • Bacteria for oil spill clean up and other environmental pollution

  11. 15.7 Designer Plants • Genetically engineered plants have been developed for pharmaceuticals, herbicide, pest, and disease resistance, larger and tastier plants, fruits, and vegetables with greater yields • Corn, cotton, potato, soy bean, etc

  12. 15.8 Gene Transfers in Animals • Cloning holds promises for future • Clone organs and tissues • Possibly modify animals to be more disease resistant and produce greater quantities of products • Not currently occurring in farm animals

  13. 1997 – the first animal was cloned – Dolly a lamb • 1. Remove nucleus from cell • 2. Transfer nuclei from desired cells into unfertilized eggs • 3. Implant the “zygote” into surrogate mother • Since Dolly – we have cloned mice, rats, cows, cats, mules, horses, and Rhesus monkeys along with a couple of endangered animals

  14. Human Genome • HGP – an int’l effort to map and sequence all human genes • 15 countries started 11/1/90 and finished 4/25/03 (50 years after Watson & Crick paper published) • 1. Genome – only 30,000 genes so it took less time • Includes mapping & sequencing of other species for comparison • 2. RNA transcription – more difficult since 30,000 genes code for 80,000 proteins due to alternative splicing • 3. Proteome – quest for every human protein

  15. 15.9 Who Gets Enhanced? • HGP already has an ethics committee due to insistence of James Watson • HGP needs to be used to help people and must be regulated by laws • Must prevent invasion of privacy and discrimination by insurance companies, employers,etc. • Must prevent Eugenics: purging of “undesirable” traits from human population (Hitler) • Science provides society with knowledge and opportunities – society requires rules and constraints to prevent abuse

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