Download Genetically Engineered Foods

Genetically Engineered Foods
Techniques, Benefits and Risks
Genetically Engineered Foods
Background on Genetic Engineering
Methods of transferring genetic material
Traits of genetically altered plants
Traits of genetically altered animals
Environmental and health concerns
Regulation in the U.S.
Background
Goal: to introduce, enhance or delete a
particular characteristic
plant breeding, hybridization
recombinant DNA technology: specific
genetic fragments isolated and inserted in
a different organism - accomplished
through alteration of DNA
Basics of Genetic
Engineering
DNA molecule: double helix structure
strands consisting of sugars and phosphates
series of bases arranged along the strands: Adenine,
thymine, cytosine, and guanine
sequence of bases determined the specific
characteristics of the organism
Transcription: resulting in mRNA, which is a
reverse copy
Translation: tRNA carrying amino acids connect
to mRNA
Recombinant DNA
Technology
Enzymes: proteins used to catalyze
specific reactions many derived from bacteria used as tools
to manipulate DNA
“Gene Splicing”
Restriction Enzymes: cuts DNA, leaves
“sticky” ends which attach to bases of DNA
from another source
Ligase Enzymes: creates strong bond
Methods of Transferring
Genetic Material
Vector: vehicle for transfer
usu. Bacterial plasmids
Agrobacterium is most common: natural soil
bacterium causing crown gall disease in plants by
inserting part of its own plasmid into the host DNA
GEs encode and clone desired trait in lab, incorporate
into plasmid and infect plant
seeds of infected plant grow plant with engineered
trait
But, can’t be used on monocots (rice, wheat, maize)
only on dicots (potatoes, tomatoes, soybeans)
Methods of Transferring
Genetic Material (cont’d)
Vectorless transmission
Gene guns: fire tiny metal particles coated with DNA
into tissue culture of cells
direct injection into nucleus - generally used for
genetic engineering of animals
Gene Silencing: suppression of gene to
prevent expression of protein
Marker Genes: used to determine successful
transformation - luciferase, antibiotic
resistance markers
Traits of Genetically
Altered Plants
Herbicide Resistance:
spraying herbicides to kill weeds can also injure crops
herbicides are broken down naturally by bacteria in
soil
GEs transfer detoxifying enzymes from soil bacteria
to plants
2 methods: (1) genes that express proteins that
degrade the herbicide (2) alter sensitivity or quantity
of enzymes that an herbicide acts upon to kill plant
Monsanto’s RoundupTM-Ready Soybeans overproduce
EPSPS
Traits of Genetically
Altered Plants (cont’d)
Pest-resistance
prevents crops from having to be sprayed with costly
and hazardous chemical pesticides
Most common stratey: using genes from Bacillus
Thuringiensis (B.t.) , soil bacteria that expressed
proteins toxic to insects
biodegradable and safe for humans and non-target
organisms
1995 EPA approved sale of first B.t. commercial
crops: Monsanto’s New LeafTM potato
Limitations: specific to certain groups of insects,
trouble achieving high enough levels of toxins
Traits of Genetically
Altered Plants (cont’d)
Disease resistance and stress tolerance
GE also to create resistance to disease-causing
viruses, bacteria and fungi
Resistance to conditions such as frost and drought
gene from Winter Flounder, Arctic fish, inserted
into potato and tomato and increased tolerance to
cold temperatures
Traits of Genetically
Altered Plants (cont’d)
Designer Foods
GE Tomato: wanted firmer, redder
2 methods of gene silencing:
• suppress the gene expressing PG, the enzyme
responsible for breaking down the cell walls
• suppress the gene that expresses ethylene, which
promotes the ripening process
Other traits: sweeter berries, higher levels of
protein in vegetables
Other uses for GE crops: cotton for blue jeans
Traits of Genetically
Altered Animals
Genes transferred to animals generally produce
growth hormones
Recombinant BST: GE in cows to increase milk
production
Humans: linked to higher levels of insulin grown
factor-1, which may trigger premature grown in
infants and breast cancer
animal: promotes increase in mastisis and other
fertility disorders
Other traits: lower fat levels and increased
disease resistance in animals
Concerns
Ecological Risks
Transgenic crops will become “weeds”
will act like exotic species and invade other areas
Genes will escape into other plants that will become
weeds
hybridization with wild relatives and create
“superweeds”
Pests will develop resistance to pesticide-producing
plants
concern over loss of B.t. as an insecticide
Concerns (cont’d)
Human Health Concerns
increase in allergic reactions when genes
from other foods or animals that express
certain proteins are transferred
antibiotic resistance marker genes may be
transferred to bacteria that lives in the gut of
humans and animals - may reduce the
effectiveness of antibiotics
Concerns: (cont’d)
Other concerns
impact on farmers, particularly in developing
countries
Not able to use seeds from one year to next:
patenting and “Terminator”
Ethical/moral concerns
religious groups unable to eat certain foods
vegetarians
welfare of animals
playing with “Mother Nature”
Regulation
GE foods regulated by 3 different agencies:
USDA, FDA, EPA
apply several different statutes, not one
comprehensive law regulating
Many claim “patchwork” approach is not
ensuring the safety of these products
Survey conducted: 97% of Americans want
labeling of GE foods
Regulation should not be left to the industry