Presentation on theme: "Genetically Modified Foods"— Presentation transcript:
1 Genetically Modified Foods The essential questions?What ethical issues arise from genomic manipulation?What are the societal implications?How do scientist manipulate DNA and the genome of an organism?Project ARISE: Advancing Rhode Island Science EducationFunding provided by a Science Education Partnership Award from the NationalCenter for Research Resources
2 Genetically Modified Foods Student will know:Students who complete this unit should have a better understanding of thetechnology used to develop GM foods and any potential risks and benefitsof genetically modifying organisms.Project ARISE: Advancing Rhode Island Science EducationFunding provided by a Science Education Partnership Award from the NationalCenter for Research Resources
3 Genetically Modified Foods Students should ask:Do we have enough information on GM foods to make an informed decision tosupport or reject GM foods?Project ARISE: Advancing Rhode Island Science EducationFunding provided by a Science Education Partnership Award from the NationalCenter for Research Resources
5 OutlineHow to make a GM organismTechniquesHomework for tonight
6 Have you ever eaten genetically modified food? Can you tell the difference between a genetically modified organism and a non-GM organism?Do GM foods taste any different? Could they?
7 What is genetic modification? Does genetic modification only happen in plants?No, the first gene was transferred into bacteria.What are some reasons for genetic modification?Express recombinant insulin in bacteriaWhat are some of the benefits and some of the disadvantages of GM foods?
8 How long have humans been genetically modifying organisms? TeosinteWhat about in the lab? How long have scientists been modifying organisms?How is modern technology used to genetically modify organisms?
9 Why would we want to modify an organism? Better crop yield, especially under harsh conditionsHerbicide or disease resistanceNutrition or pharmaceuticals, vaccine delivery“In 2004, approximately 85% of soy and 45% of corn grown in the U.S. were grown from Roundup Ready® seed.”OER open education resources
10 Roundup Ready Gene“The glyphosate resistance gene protects food plants against the broad-spectrum herbicide Roundup®, which efficiently kills invasive weeds in the field. The major advantages of the "Roundup Ready®” system include better weed control, reduction of crop injury, higher yield, and lower environmental impact than traditional weed control systems. Notably, fields treated with Roundup® require less tilling; this preserves soil fertility by lessening soil run-off and oxidation.”
11 How to make a GM organism Clone gene into vector (i.e. plasmid) with restriction enzymes and other molecular techniquesTransform into organism or into biological vector (agrobacteria or virus)Infect plant with bacteriaSelect for transformants with herbicide
12 What we are doing today Extract DNA from plant or food product Use the technique of PCR to copy a region of DNA found in Round-Up Ready foodsTomorrow we will analyze these products with gel elecrophoresis
13 Many of the same techniques are used to make a genetic modifications as to detect one Polymerase Chain Reaction (PCR)Restriction enzymesGel electrophoresisTransformation
14 PCRInvented in 1983 by Kary Mullis (Nobel Prize in 1993 for its discovery)Uses primers to exponentially amplify a specific region of DNAComponents needed for the reaction:DNAPrimers to region of interestDNA polymerase (Taq – used to synthesize the DNA)dNTPS (the building blocks of the copied DNA)Buffer (with appropriate salts to ensure the enzyme works properly)
15 PCR Three steps of the reaction: Denaturation: High heat (94-98o) to separate the strands of DNAAnnealing: (50-60o – depends on the primers) this step allows the primers to bind to the denatured DNA strandsElongation (74o) – DNA polymerase synthesizes the new strandThis step is dependant on the length of the product to be amplified (1min/1kb of DNA)Check products with gel electrophoresis and sequencing
19 PCR: Applications Used to test for gene products for disease diagnosis Used to amplify small amounts of materialForensicsFossil RecordsUsed for recombinant DNA technologyUsed for virus detection
20 Resources Potential Problems No amplification due to wrong buffer conditionsNo amplification due to lost enzyme activityPrimers are wrongOnline Resources:Click on TechniquesPCR is found in amplifying
22 Restriction EnzymesRestriction enzymes are also called restriction endonucleasesThey cut double stranded DNA at sequence specific sitesThey can produce “sticky ends” or “blunt ends” depending on the enzymeSticky EndsBlunt EndsSticky EndsBlunt Ends
23 Restriction Enzymes1978 Nobel Prize in Medicine was awarded to Daniel Nathans and Hamilton Smith for the discovery of restriction endonucleasesRestriction enzymes were discovered in E.coli as a defense mechanism against bacterial viruses (bacteriophages)The recognition sites are usually 4-12 nucleotides longSequences are palindromic (GAATTC)There are hundreds of restriction enzymes currently being used
24 Restriction EnzymesWhat is better for making recombinant DNA: Sticky ends or blunt ends?
25 Restriction Enzymes Student activity Potential Problems: Wrong buffer* activityOnline resourcesClick on TechniquesRestriction enzymes are found in cutting and pasting
26 Gel ElectrophoresisGel electrophoresis is used to separate nucleic acids (DNA and RNA) or proteins for analytical useDNA and RNA are separated using agaroseProteins are separated using polyacrylamideThe gel is a matrix (cross-linked polymers) that allow products to be separatedSeparation is based on the size (based on charge) of a product as it moves through a charged fieldWhat is the charge on DNA and proteins? What is the shape? Why is this important?How would you connect the electrodes?
27 Gel ElectrophoresisThe negative charge is at the top (closest to the samples) and the positive charge is at the bottomSamples are negatively charged and will travel towards the positive chargeDNA and RNA are negative because of their sugar-phosphate backboneProteins are denatured to give a constant shape and given a charge through the negative loading buffer usedSamples are diluted in a loading buffer that helps the samples stay in the wells
34 Gel Electrophoresis Online Resources: http://www.dnai.org/b/index.html Potential ProblemsConnecting the charges backwardNot enough loading dyeRunning the gel too hotHandling EtBrOnline Resources:Click on TechniquesGel electrophoresis is found in sorting and sequencing
35 Homework Activate your Brown ID: http://activate.brown.edu Read “Teaching High School Science Chapters 1 and 2Read “GM foods & Teaching Critical Thinking”Read GM Foods Unit and list three concerns or questions regarding the unit.
37 Restriction Enzymes: Applications Restriction enzymes are commonly used in laboratories to create recombinant DNAHarvest DNA products for other applicationsDNase a general nuclease used to eliminate DNA in RNA samples