|Plants & Human Affairs (BIOL106) - Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; email@example.com; http://www.employees.csbsju.edu/ssaupe|
Transgenic (=Genetically Modified) Crops
I. Transgenic Plants
contain genes from another plant
genetically modified � or GM crop
in a sense, all crops are genetically modified from wild state by process of domestication via selective breeding and selection
B. How to make a transgenic plant?
DNA isolated → restriction enzyme cuts up DNA → pieces of DNA isolated with gene of interest → DNA sequence modified to include markers (punctuation marks, add a promoter and termination sequence) → insert into plant → select transgenic individuals → regenerate new plant
C. Inserting Genes
Gene �gun� (especially used in corn and rice)
Ti plasmid � from Agrobacterium tumefaciens, causes crown gall, can insert its DNA into host plant which becomes incorporated into host chromosome
D. Selecting genetically modified
Only a small percentage of treated cells/plants actually become genetically modified by the process. Thus, these must be identified. Usually associate a marker gene with the gene construct. This marker is usually for antibiotic or herbicide resistance. If the cell/plant was transformed by the transgene, then it will survive when grow on a medium containing antibiotic or herbicide.
II. Regulation of GMO�s
institutional safety committees
USDA � APHIS (federal plant pest act; regulate organisms likely to become pests/weeds
FDA � oversees safety of foods
EPA � regulate for pest resistance
World Trade Organization � regulates commerce/sale
III. Examples of GMO�s
Roundup resistant crops
Bt crops � Bacillus thuringensis contains a gene
called Cry that produces a crystalline protein. Once eaten, in an animal
gut is is converted to a toxin (endotoxin) that kills assorted insects
including maize corn borer, tobacco budworm and others on cotton, Colorado
potato beetle. The Good News � dramatic reduction in amount of chemicals
used on fields. The Bad News � can potentially kill monarchs (see case
study) and possibility of resistance gene spreading.
One way to avoid resistance, farmers required to plant 20% of fields in non-Bt corn so that there will be large enough population of Bt susceptible species to mate with and swamp out any Bt resistant individuals.
Lots of others
IV. Potential Problems
A. Human health issues
transfer of antibiotic resistance to other organisms
enzymes could inactivate antibiotics
C. Impact on crop technology
V. Some ethical issues
Gene that cause the embryo to die. The main purpose is to protect the patent so farmer can�t collect seeds and replant without buying more genetically modified crops.
Pro � crops won�t spread, companies protect patent
Con � if spreads, kills embryo of neighboring plants (crop and wild), small farmers can�t afford
VI. Risk/Benefit Analysis
A. Risk assessment - Identify and define risks
What could go wrong?
How likely it is to occur?
How harmful if it does?
B. Risk = hazard x exposure; amount of risk = (hazard x exposure)/safeguards
Does it save lives or is an improvement?
Does it improve quality of life?
Does it solve a problem?
Does it increase efficiency?
Who derives a benefit?
D. Information Analysis
Is it information vs. propaganda?
Peer-reviewed vs. other?
Last updated: 03/18/2005 � Copyright by SG Saupe