Genetically Modified Foods WHY MODIFY Increase freshness decrease

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? • 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)

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

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

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

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

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

PCR

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

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

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

“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

ELECTROPORATION • A jolt of electricity is used to puncture selfrepairing 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

• 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

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

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

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)

WEBSITES • http: //www. agresearch. co. nz/scied/search/bi otech/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/

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

MORE GREAT WEBSITES • http: //www. biotechknowledge. monsanto. com /biotech/bbasics. nsf/genetrans. html? Open. Page – Good overview of gene insertion • http: //ornl. gov/sci/techresources/Human_Ge nome/elsi/gmfood. shtml • http: //ohioline. osu. edu/hygfact/5000/5058. html