Recombinant DNA and Genetic Engineering


Genetic engineering is the ultimate manipulation of nature. We now have the technology to cure disease and create life. Are we too busy wondering what we can do with this knowledge that we aren't stopping to ask if we should..?

  1. Recombination in Nature–and in the Laboratory
    1. For approximately 3.5 billion years, mutation, crossing over, random gene mixing at fertilization and hybridizations between species have contributed to the diversity of life on earth.
    2. Through artificial selection of animals and plants, humans have been manipulating the genetic character of many species for thousands of years.
    3. Today, we can "engineer" genetic changes through recombinant DNA technology.
      1. DNA from different species can be cut, spliced together, and inserted into bacteria which then multiply the DNA necessary for protein production.
      2. Genetic engineering has great promise for agriculture, medicine, and industry, but it has also raised ecological, social, and ethical questions.
    4. Plasmids, Restriction Enzymes, and the New Technology
      1. Bacterial cells have a single chromosome, a circular piece of DNA.
      2. Some bacteria also have plasmids, which are circular DNA, or RNA, molecules that carry only a few genes and can replicate independently of the single "main" chromosome.
      3. Many bacteria can transfer plasmid genes to other bacteria, transforming the recipient’s chromosome into a recombinant DNA molecule.
      4. Viruses can also participate in gene transfers.
    5. Producing Restriction Fragments
      1. Bacteria possess restriction enzymes whose usual function is to cut apart foreign DNA molecules.
  2. Working with DNA Fragments
    1. Amplification Procedures
      1. PCR

    2. Sorting Out Fragments of DNA
      1. Gel electrophoresis can be used to separate restriction fragments according to their size using electrical current.

      2. After the DNA fragments have been sorted out according to length, researchers can determine the nucleotide sequence of each using techniques such as the Sanger method.
  3. Genetic Engineering of Animals
    1. Applying the New Technology to Humans
      1. Researchers have embarked on the Human Genome Project to map all of the human chromosomes by sequencing the approximately 3 billion nucleotides.
      2. This project could enhance the field of genetic therapy, the transfer of modified genes into the body to correct a genetic defect or boost resistance to disease.

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