recombinant dna (part 3)

• DNA technology


  The manipulation of genes for some practical purpose
• DNA structure and function


  • How DNA passes from generation to generation
• Manipulate DNA


  1. Copy it

  2. Figure out its sequence of nucleotides

  3. Switch it on and off

  4. Search for specific pieces of it inside a living cell
• Moving a gene from one cell to another

  Comparisons among multiple genomes
• Recombinant DNA


  • Genetic material that has been spliced together from multiple sources
• Transgenic organism


  An individual that receives recombinant DNA
• Transgenic bacteria and yeasts

  • Produce dozens of drugs such as human insulin, blood clotting factors, immune system biochemicals, and fertility hormones
  • Produce a milk-curdling enzyme called chymosin used by many U.S. cheese producers
• Transgenic animals


  • Can reveal how a disease begins
  • Can secrete human proteins in their milk
  • Engineered for rapid growth
• Some object to the "unnatural" practice of combining genes from organisms that would never breed in nature
• Others fear that ecological disaster could result if genetically modified organisms spread their new genes to the wild species
• Others worry that unfamiliar protein combinations in transgenic crops may result to food allergies
• Genetically modified seeds may be expensive; farmers might be unable to afford them
• DNA Sequencing


  1. The DNA Polymerase enzyme makes complementary copies of an unknown DNA sequence

  2. The copies are terminated early, thanks to chemically modified "terminator" nucleotides

  3. Sorting the fragments by size reveals the sequence
• Only about 1.5% of the human genome sequence actually encodes protein
• Introns


  Removing different combinations of introns from an mRNA molecule making cells produce several proteins from one gene
• Some of the 98.5% of the human genome consists of regulatory sequences that control gene expression
• DNA is also transcribed to rRNA and tRNA
• Chromosomes also contain pseudogenes–DNA sequences that are very similar to protein–encoding genes that are transcribed but whose mRNA is not translated into protein
• Polymerase chain reaction (PCR)


  Rapidly produces millions of copies of a selected DNA sequence in a test tube
• Applications of PCRs


  • Trace amounts of DNA extracted from a single hair follicle or few skin cells left at a crime can yield enough genetic material to reveal a person's unique DNA profile
• DNA profiling


  Uses the most variable parts of the genome to detect genetic differences between individuals
• Short tandem repeats (STRs)


  Most common approach to DNA profiling; sequences of a few nucleotides that are repeated in noncoding regions of DNA
• Stem cell


  Any undifferentiated cell that can give rise to specialized cell types
• Embryonic stem cells


  Give rise to all cell types in the body (including adult stem cells); also called as "totipotent"
• Adult stem cells


  More differentiated and produce a limited subset of cell types; "pluripotent" (ex: stem cells in the skin, bone marrow stem cells)
• Clones


  Genetically identical individuals, that detach and live independently
• Cloning


  Asexual reproduction; division of a single cell: One individual becomes two
• Top causes of death: heart disease, stroke, cancer and infection
• Some ailments entirely caused by mutated alleles: hemophilia, Tay-Sachs syndrome and sickle cell disease
• DNA probe


  A single-stranded sequence of nucleotides that is used to detect a complementary DNA sequence
• Preimplantation genetic diagnosis (PGD)


  Can reduce the odds of having an affected child by screening embryos for the disease-causing allele
• Gene therapy


  Provides new treatment options to incurable diseases by adding healthy DNA to a person's cell
• DNA technology can prevent and reduce human suffering: improves chance of having healthy children, detects diseases early, offers prospect of new treatments
• Should the techniques be available only to the wealthy?
• Does the morality of a woman's decision depend on the severity of the illness? Should we reserve fetal screening for life-threatening illnesses or is it morally permissible to use it for milder conditions?
• Once the technology is perfected, how should it be used? Only for debilitating diseases or less serious conditions as well?
• Is it right to use the techniques of gene therapy to enhance a person's appearance or athletic performance?
• What about altering the DNA of a person's germ line so future generations contain the new gene?