chapter 07

Genomics and biotechnology

Genetic engineering technologies have introduced genetically modified organisms that provide new opportunities and risks.

Genetic engineering allows genes from one species to be expressed in another.
Restriction enzymes allow a desired piece of DNA from one species to be inserted into that of another - producing recombinant DNA.
Brief summary:

In 1982, human insulin was produced by bacteria - a transgenic organism, or Genetically Modified Organism (GMO).

Restriction enzymes can be used to isolate genes of interest.
1. A gene of interest from a target organism is identified.
2. A restriction enzyme can cut DNA double helixes at specific restriction sites that contain a palindrome sequence.
3. The restriction enzyme binds and cuts DNA at the restriction sites.
4. DNA fragments with complementary single-stranded ends are produced. Some of these fragments contain the genes of interest.
After isolation, restriction fragments can reform double helixes with other sources of DNA to produce recombinant DNA.
Review:

Humans have long used artificial selection techniques to enhance crops and animals.
Genetic engineering of Genetically Modified Organisms has radically sped up this process.
- Bt corn
- Golden rice



Caterpillars can damage corn crops. Bt extracted from a bacterium (Bacillus thuringiensis) is a pesticide that is toxic to caterpillars.	The Bt gene can be inserted into the corn genome to yield a GMO corn with built-in pest resistance.	Farmers no longer need to spray crops with the Bt pesticide.

Golden Rice is a variety with genes from other organisms added to it to produce beta-carotene, which is a precursor for vitamin A.
This transgenic crop (or genetically modified organism - GMO) has the potential for reducing vitamin A deficiency in developing countries where the major staple food is rice.

Mammals can be cloned by nuclear transfer.
- Cloning Dolly by nuclear transfer
  1. The nuclei are removed from a mammary cell of a female lamb and an egg cell from a different female.
  2. The nucleus from the mammary cell is implanted into the egg cell.
  3. An electric shock is applied to the egg to trigger cell division, which can happen in culture for a few divisions.
  4. The embryo is implanted into a living uterus; a 3rd lamb serves as the surrogate mother.
  5. The cloned Dolly is identical in genetic makeup to the mammary cell donor.
  - What's wrong with this picture?
    - Dolly should look identical to the mammary cell donor. Tutorial:
DNA fingerprinting makes use of several genetic technologies.
- Short tandem repeats provide genetic markers.
  - Human DNA contains highly variable regions called short tandem repeats (STRs) within non-coding DNA.
    The number of repeats vary greatly among individuals, yielding many different alleles of each STR in the population.
    A total of 13 different STR locations can be used to uniquely identify an individual based on the combination of her STRs.
    (tandem: one following or behind the other)
- Gel electrophoresis separates DNA fragments.
  - Electrophoresis
    DNA samples are cut into fragments by restriction enzymes.
    The fragments are placed in a semifluid gel apparatus and an electrical charge is applied.
    The negatively charged DNA fragments move toward the positive end at different speeds, based mainly on fragment size.
    The separated fragments can be visualized with dyes.
- DNA fingerprints can identify individuals based on their DNA.
- DNA fingerprint
  DNA fragments created by restriction enzymes and separated by Electrophoresis are analyzed to identify an individual.
  The first criminal conviction using DNA fingerprinting was in 1987, when the fragments from a suspect matched perfectly with those collected from victims.
  Review: