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Genetically Modified Foods

Genetic modification (GM) involves altering a plant’s genome to enhance traits such as increased crop yield, freshness, and resistance to pests. This process includes isolating and inserting foreign genes into plants, leading to the production of crops with desired characteristics, like larger fruits and higher vitamin content. Various methods such as transformation, electroporation, and the gene gun technique are employed for modification. While GM crops offer significant agricultural benefits, they also raise ethical, economic, and environmental concerns that merit careful consideration.

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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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