Genetically Modified FoodsGenetically Modified Foods

WHY MODIFY? WHY MODIFY?

• Increase freshness (decrease rate of Increase freshness (decrease rate of decay)decay)

• Increase vitamin contentIncrease vitamin content• Pesticide resistancePesticide resistance• Increase crop yield Increase crop yield • Larger fruits/vegetablesLarger fruits/vegetables• Shift growing seasonShift growing season• Etc….Etc….

WHAT IS GENETIC WHAT IS GENETIC MODIFICATION?MODIFICATION?

• An alteration of the plant’s genome – An alteration of the plant’s genome – injection of hormones or antibtiotics is injection of hormones or antibtiotics is NOT an example of genetic modificationNOT an example of genetic modification

• A foreign gene is inserted into the A foreign gene is inserted into the plant’s genomeplant’s genome

• Gene then codes for a specific protein Gene then codes for a specific protein (e.g. antibiotic resistance)(e.g. antibiotic resistance)

HOW ARE PLANTS MODIFIED?HOW ARE PLANTS MODIFIED?

• Series of stepsSeries of steps– Isolation of desired gene (mapping)Isolation of desired gene (mapping)– Gene cut from genome (restriction Gene cut from genome (restriction

enzymes)enzymes)– Gene amplified through PCR Gene amplified through PCR

(polymerase chain reaction)(polymerase chain reaction)– Target gene incorporated into plant Target gene incorporated into plant

(transformation)(transformation)– Plant produces seeds with new genePlant produces seeds with new gene

GENE MAPPINGGENE MAPPING

• ReviewReview– Recombination frequency = map unitsRecombination frequency = map units– Linkage map (relative location)Linkage map (relative location)– Cytological mapCytological map

RESTRICTION ENZYMESRESTRICTION ENZYMES

• Molecular scissorsMolecular scissors• Cut DNA in specific places (bp Cut DNA in specific places (bp

sequences)sequences)• Leaves “sticky ends” which can be Leaves “sticky ends” which can be

joined with DNA ligasesjoined with DNA ligases

POLYMERASE CHAIN REACTIONPOLYMERASE CHAIN REACTION

• PCR can be used to make copies of PCR can be used to make copies of selected segments of available DNAselected segments of available DNA

• PCR needsPCR needs– DNA molecule or fragmentDNA molecule or fragment– Nucleotides - all fourNucleotides - all four– DNA polymeraseDNA polymerase– PrimersPrimers

PCRPCR

• Primer - an artificially made single-Primer - an artificially made single-stranded sequence of DNA required for stranded sequence of DNA required for the initiation of replicationthe initiation of replication

• When all ingredients are combined and When all ingredients are combined and heated, DNA will double every 5 heated, DNA will double every 5 minutesminutes

PCRPCR

PCRPCR

• Heating the DNA separates the strandsHeating the DNA separates the strands• DNA polymerase from a thermophilic DNA polymerase from a thermophilic

bacterium is used because it is not bacterium is used because it is not adversely affected by the heating adversely affected by the heating processprocess

• Drawback - sensitivity so samples can Drawback - sensitivity so samples can be easily contaminatedbe easily contaminated

TRANSFORMATIONTRANSFORMATION

• Genetic engineering of plants easier Genetic engineering of plants easier than animalsthan animals– Natural transformation system for plants Natural transformation system for plants

(bacterium (bacterium Agrobacterium tumefaciensAgrobacterium tumefaciens))– Plant tissue can redifferentiate (a Plant tissue can redifferentiate (a

transformed piece of leaf can transformed piece of leaf can regenerate to a whole plant)regenerate to a whole plant)

– plant transformation & regeneration are plant transformation & regeneration are relatively easy for a variety of plantsrelatively easy for a variety of plants

BACTERIAL TRANSFORMATIONBACTERIAL TRANSFORMATION

• Soil bacterium Soil bacterium A. tumefaciensA. tumefaciens can can infect wounded tissue & transfer large infect wounded tissue & transfer large plasmid (Ti plasmid)plasmid (Ti plasmid)

• Genes from Ti plasmid integrated into Genes from Ti plasmid integrated into the plant chromosome are expressed at the plant chromosome are expressed at high levelshigh levels

““SHOTGUNNING”SHOTGUNNING”

• DNA can be delivered into the cells by DNA can be delivered into the cells by small, µm-sized tungsten or gold bullets small, µm-sized tungsten or gold bullets coated with the DNAcoated with the DNA

• Device uses a sudden change in Device uses a sudden change in pressure of He gas to propel the pressure of He gas to propel the particlesparticles

• ““Gene gun” or “shotgun” techniqueGene gun” or “shotgun” technique

ELECTROPORATIONELECTROPORATION

• A jolt of electricity is used to puncture A jolt of electricity is used to puncture self-repairing holes in protoplasts (the self-repairing holes in protoplasts (the cell without the cell wall), DNA can get cell without the cell wall), DNA can get in through holesin through holes

• Often difficult to regenerate fertile Often difficult to regenerate fertile plants from protoplasts of cerealsplants from protoplasts of cereals

• Significant advances in overcoming Significant advances in overcoming these practical difficulties have been these practical difficulties have been made over the yearsmade over the years

• Essentially all major crop plants can be Essentially all major crop plants can be (and have been or are being) (and have been or are being) genetically engineeredgenetically engineered

• Procedures are now routine and the Procedures are now routine and the frequency of success is very highfrequency of success is very high

PROBLEMS?PROBLEMS?

• Expense Expense – OK for Monsanto, but not for a local OK for Monsanto, but not for a local

farmer or a poor countyfarmer or a poor county

• Consumer perceptionsConsumer perceptions– But haven’t humans always had a hand But haven’t humans always had a hand

in manipulating our crops?in manipulating our crops?

• LabelingLabeling• EthicsEthics

IDEAS FOR PRESENTATIONIDEAS FOR PRESENTATION

• You can design your presentation to You can design your presentation to incorporate different issues incorporate different issues

• Issues for you to think about/address Issues for you to think about/address (include all, one, none, etc):(include all, one, none, etc):– Economic impact Economic impact – Environmental impactEnvironmental impact– Health concerns – include relevant Health concerns – include relevant

research research

MORE IDEAS…MORE IDEAS…

• Choose a “side”Choose a “side”– Play the role of an organic farmer or an Play the role of an organic farmer or an

agricultural biotech firm and persuade agricultural biotech firm and persuade your classmates!your classmates!

• Debate format (group of 3) Debate format (group of 3)

WEBSITESWEBSITES

• http://www.agresearch.co.nz/scied/http://www.agresearch.co.nz/scied/search/biotech/search/biotech/gene_gmomaking_plant.htmgene_gmomaking_plant.htm– How to genetically modify a plantHow to genetically modify a plant

• http://www.food.gov.uk/gmfoods/http://www.food.gov.uk/gmfoods/– Lots of information!Lots of information!

• http://scope.educ.washington.edu/http://scope.educ.washington.edu/gmfood/gmfood/

WEBSITESWEBSITES

• http://www.biotechknowledge.monsanthttp://www.biotechknowledge.monsanto.com/o.com/

• http://www2.dupont.com/http://www2.dupont.com/Biotechnology/en_US/index.htmlBiotechnology/en_US/index.html– 2 large agricultural firms that currently 2 large agricultural firms that currently

use GE foodsuse GE foods– Supply a LARGE % of American produceSupply a LARGE % of American produce

MORE GREAT WEBSITESMORE GREAT WEBSITES

• http://www.biotechknowledge.monsanthttp://www.biotechknowledge.monsanto.com/biotech/bbasics.nsf/gene-trans.hto.com/biotech/bbasics.nsf/gene-trans.html?OpenPageml?OpenPage– Good overview of gene insertion Good overview of gene insertion

• http://ornl.gov/sci/techresources/http://ornl.gov/sci/techresources/Human_Genome/elsi/gmfood.shtmlHuman_Genome/elsi/gmfood.shtml

• http://ohioline.osu.edu/hyg-fact/http://ohioline.osu.edu/hyg-fact/5000/5058.html 5000/5058.html