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Genetically Modified Foods

Genetically Modified Foods. WHY MODIFY?. Increase freshness (decrease rate of decay) Increase vitamin content Pesticide resistance Increase crop yield Larger fruits/vegetables Shift growing season Etc…. WHAT IS GENETIC MODIFICATION?.

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Genetically Modified Foods

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  1. Genetically Modified Foods

  2. WHY MODIFY? • Increase freshness (decrease rate of decay) • Increase vitamin content • Pesticide resistance • Increase crop yield • Larger fruits/vegetables • Shift growing season • Etc….

  3. WHAT IS GENETIC MODIFICATION? • An alteration of the plant’s genome – injection of hormones or antibtiotics is NOT an example of genetic modification • A foreign gene is inserted into the plant’s genome • Gene then codes for a specific protein (e.g. antibiotic resistance)

  4. HOW ARE PLANTS MODIFIED? • Series of steps • Isolation of desired gene (mapping) • Gene cut from genome (restriction enzymes) • Gene amplified through PCR (polymerase chain reaction) • Target gene incorporated into plant (transformation) • Plant produces seeds with new gene

  5. GENE MAPPING • Review • Recombination frequency = map units • Linkage map (relative location) • Cytological map

  6. RESTRICTION ENZYMES • Molecular scissors • Cut DNA in specific places (bp sequences) • Leaves “sticky ends” which can be joined with DNA ligases

  7. POLYMERASE CHAIN REACTION • PCR can be used to make copies of selected segments of available DNA • PCR needs • DNA molecule or fragment • Nucleotides - all four • DNA polymerase • Primers

  8. PCR • Primer - an artificially made single-stranded sequence of DNA required for the initiation of replication • When all ingredients are combined and heated, DNA will double every 5 minutes

  9. PCR

  10. PCR • Heating the DNA separates the strands • DNA polymerase from a thermophilic bacterium is used because it is not adversely affected by the heating process • Drawback - sensitivity so samples can be easily contaminated

  11. TRANSFORMATION • Genetic engineering of plants easier than animals • Natural transformation system for plants (bacterium Agrobacterium tumefaciens) • Plant tissue can redifferentiate (a transformed piece of leaf can regenerate to a whole plant) • plant transformation & regeneration are relatively easy for a variety of plants

  12. BACTERIAL TRANSFORMATION • Soil bacterium A. tumefaciens can infect wounded tissue & transfer large plasmid (Ti plasmid) • Genes from Ti plasmid integrated into the plant chromosome are expressed at high levels

  13. “SHOTGUNNING” • DNA can be delivered into the cells by small, µm-sized tungsten or gold bullets coated with the DNA • Device uses a sudden change in pressure of He gas to propel the particles • “Gene gun” or “shotgun” technique

  14. ELECTROPORATION • A jolt of electricity is used to puncture self-repairing holes in protoplasts (the cell without the cell wall), DNA can get in through holes • Often difficult to regenerate fertile plants from protoplasts of cereals • Significant advances in overcoming these practical difficulties have been made over the years

  15. Essentially all major crop plants can be (and have been or are being) genetically engineered • Procedures are now routine and the frequency of success is very high

  16. PROBLEMS? • Expense • OK for Monsanto, but not for a local farmer or a poor county • Consumer perceptions • But haven’t humans always had a hand in manipulating our crops? • Labeling • Ethics

  17. IDEAS FOR PRESENTATION • You can design your presentation to incorporate different issues • Issues for you to think about/address (include all, one, none, etc): • Economic impact • Environmental impact • Health concerns – include relevant research

  18. MORE IDEAS… • Choose a “side” • Play the role of an organic farmer or an agricultural biotech firm and persuade your classmates! • Debate format (group of 3)

  19. WEBSITES • http://www.agresearch.co.nz/scied/search/biotech/gene_gmomaking_plant.htm • How to genetically modify a plant • http://www.food.gov.uk/gmfoods/ • Lots of information! • http://scope.educ.washington.edu/gmfood/

  20. WEBSITES • http://www.biotechknowledge.monsanto.com/ • http://www2.dupont.com/Biotechnology/en_US/index.html • 2 large agricultural firms that currently use GE foods • Supply a LARGE % of American produce

  21. MORE GREAT WEBSITES • http://www.biotechknowledge.monsanto.com/biotech/bbasics.nsf/gene-trans.html?OpenPage • Good overview of gene insertion • http://ornl.gov/sci/techresources/Human_Genome/elsi/gmfood.shtml • http://ohioline.osu.edu/hyg-fact/5000/5058.html

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