Biol 315L Final GMO Section

• What year was the first genetically modified crop in the US released?

  1996
• GM foods


  Foods that contain components of GM crops
• GM crops


  Plants that have been genetically modified by the insertion of foreign genetic material
• Examples of GM crop traits

  pest resistance, herbicide tolerance, delayed fruit ripening, improved fruit yield, increased nutrient content, etc.
• Foreign genetic material used for GM crops is usually a gene that code for a _

  protein that gives the plant an advantage over similar crop plants
• The first step in the genetic modification process

  Identify a protein that has the potential to improve a crop.
• Bt crops 


  Popular class of GM crops that have a gene from the soil bacterium Bacillus thuringiensis inserted into their genomes, and produce a protein called delta-endotoxin (lethal to European corn borers).
• Bt toxin was first identified on

  silk farms as a toxin that kills silkworms
• The second step in the genetic modification process

  Isolate (clone) the genes that codes for the desired protein
• The third step in the genetic modification process

  Engineer the gene so that the crop plant's cells will read it correctly and manufacture the protein of interest by removing unnecessary introns and adding or changing sequences to allow the gene to be expressed. The promoter and terminator is often changed.
• Promoter


  Serves as a docking site for RNA polymerase and a signal for where it should start transcribing a gene.
• Terminator


  The signal to stop transcription
• Most common promoter used in GM crops

  35S promoter from the cauliflower mosaic virus (CaMV 35s)
• Most common terminator used in GM crops

  Nopaline synthase (NOS) terminator for Agrobacterium tumefaciens
• CaMV 35S and NOS are found in about _% of all GM crops around the world

  85
• Callus


  A clump of undifferentiated cells
• The viable insertion of the engineered gene into a plant's genome is called

  an event
• The fifth step in the genetic modification process

  to back-cross the genetically engineered crop into the most current high-yielding crop strains that are being used in the field
• The genetic modification process is very inefficient, costly and time consuming
• Arguments against GM crops

  The potential for superweeds, superbugs, allergic reactions to novel proteins, antibiotic resistance, and other unforeseen effects on public health. Concerns also include the lack of research and lack of government requirements for labeling foods in the US.
• Arguments for GM crops

  These crops are beneficial for the environment because of the reduced use of herbicides and pesticides. These crops may preserve arable land by reducing the stress on the land, improve the nutritional value of food in developing countries, and allow crops to be grown on previously unfarmable land.
• The two methods to test foods and crops to identify which contain GM genomes

  The enzyme-linked immunosorbent assay (ELISA) and using the polymerase chain reaction (PCR)
• ELISA can only test fresh produce, due to protein degradation during food processing.
• ELISA is an antibody-based test, and it identifies the specific proteins produced by GM plants.
• Since ELISA identifies the proteins produced in GMO crops, the tests must be individualized according to the type of crop.
• ELISA is inexpensive and accurate, and can be performed in the field with little experience.
• The PCR test identifies sequences of DNA that have been inserted into the GM plant.
• Since DNA is stable, it can be isolated from highly processed foods and is sufficiently intact to be amplified by PCR.
• Real-time PCR can also quantitate the percentage of GM material in a food sample.
• A single PCR test can detect 85% of all GM crops. (This is because genetic engineers use only a small number of regulatory sequences.)
• Genetically modified organism (GMO)

  An organism in which the genetic material has been altered in a way that does not occur naturally by mating and/or natural recombination
• Why have GM crops?

  Growing human population

  Loss of farmable land

  Remediation of soil

  Enrich nutrient content
• GM crop desirable traits

  • Pest Resistance

  • Herbicide Tolerance

  • Viral Resistance

  • Drought Resistance

  • Increased Nutritional Value

  • Improved Fruit

  • Altered Ripening
• Opponents argue against GM crops

  •  Creation of super pests

  •  Creation of super weeds

  • Loss of biodiversity

  • Biotechnology companies control agriculture

  • Health concerns
• Method for genetic modification of crops

  1. Choose desirable trait

  2. Clone the gene

  3. Engineer the gene

  4. Transform gene into plant

  5. Backcross GM plant into high yield crops
• Steps to test for GMOs by PCR

  1. Grind food

  2. Extract DNA from sample

  3. Test sample DNA for viable plant DNA

  4. Test sample DNA for genetic modifications
• Bio-Rad certified non-GMO food

  Verify PCR is not contaminated
• GMO positive control DNA

  Verify GMO-negative result is not due to PCR reaction not working properly
• Primers to universal plant gene (Photosystem II)

  Verify viable DNA was extracted
• Why amplify a plant gene?

  To confirm that viable DNA was extracted and that negative GM result isn’t due to a non-viable template.

  Use highly conserved chloroplast gene from Photosystem II – part of the light reaction of photosynthesis.