Genetic Modification 101

In the next couple of posts, I will take a step back and explore the process of genentic modification and its application in food products.

Genetics in a Nutshell

Deoxyribonucleic acid, or DNA, is found inside the nucleus of every cell. DNA tells the cell how to behave and carries information that is passed from generation to generation. DNA is made up of four recurring units, nucleotides or bases, arranged in pairs. The sequence of these units carries the information.[1] A gene is a specific sequence of bases that function as a unit, carrying particular “orders” for making protein in the body.[2] Genes are responsible for expression of numerous traits in living organisms.

Process of Genetic Modification

In a single sentence genetic modification is a process whereby a segment of DNA, which is found in every living cell, is extracted from one organism and spliced into a recipient organism’s preexisting DNA.[3] In this way scientists have achieved techniques for causing one organism to take up and express segments of another organism’s DNA faster than the traditional breeding methods previously employed.

There are several methods to achieve the exchange of DNA from one living organism (called the “donor”) into another(called a “host” or “recipient”). Those methods include:

  1. direct DNA uptake by the host cells mediated by chemical or electrical treatments (electro or chemical poration);
  2. microinjection of DNA directly into host cells;
  3. bioballistics, or firing tiny metal particles coated with the DNA of interest into host cells; and
  4. employing plasmids found in bacteria, such as the soil bacterium Agrobacterium tumefaciens, or a virus, as a vehicle to carry the DNA into host cells.

A Closer Look At Each Method

The electro or chemical poration method is a direct gene transfer which involves creating pores in the cell membrane to allow for the entry of the new gene.

The second method, microinjection, involves injection of DNA directly into host cells. Where the cell is large enough, as many plant and animal cells are, the injection can be done with a fine-tipped glass needle and somehow the injected genes find the host cell genes and incorporate themselves among them.

In bioballistics, the third method, a type of bio gun is used to shoot the DNA into the host cell.[4] Scientists coat thousands of tiny shards of tungsten or gold with the new genes and shoot the projectiles into the host cell, hoping that the DNA will be carried to the host cells nucleus.[5] These techniques are imprecise and depend on luck for success. [6]

The fourth method used to create a GMO is recombitant DNA (rDNA). This method uses plasmids and viruses, two biological vehicles, to carry genetic material into host cells.[7] As the Union of Concerned Scientists describes, plasmids are small circular pieces of genetic material found in bacteria that have the ability to cross species boundaries. The circles can be broken and new genetic material added to them. Plasmids augmented with new genetic material can move across microbial cell boundaries and place the new genetic material next to the bacterium’s own genes. Often the bacteria will take up the gene and begin to produce the protein for which the gene codes.

Similarly, viruses can also act as vectors in genetic engineering. Viruses are infectious particles that contain genetic material to which a new gene can be added. The virus can carry the new gene into a recipient cell in the process of infecting that cell. The virus can also be disabled so that while it can carry a new gene into a cell, it cannot redirect the cell’s genetic machines to make thousands of copies of itself.

Read the fact sheet on genetic engineering techniques prepared by the Union of Concerned Scientists for additional details.

[1] Jeffrey M. Smith, Seeds of Deception: Exposing Industry and Government Lies About the Safety of the Genetically Engineered Foods You’re Eating, 49 (Yes! Books 2003)
[2] Id. See also DNA From the Beginning, A Gene is a Discrete Sequence of DNA Molecule (last visited July 19, 2009).
[3] John Charles Kunich, Mother Frankenstein, Doctor Nature, and the Environmental Law of Genetic Engineering, 74 S. Cal. L. Rev. 807, 809 (2001).
[4] Sophia Kolehmainen, Precaution Before Profits: An Overview of Issues on Genetically Engineered Food and Crops, 20 Va. Envtl. L.J. 267, 271 (2001).
[5] Smith, supra note 1, at 57.
[6] Kolehmainen, supra note 4, at 271.
[7] Kolehmainen, supra note 4, at 272.