GeneticallyModifiedFoodsWeek2

GeneticallyModifiedFoodsWeek2 - C118 Laboratory -...

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1 C118 Laboratory - Genetically Modified Foods Biotechnology Explorer GMO Foods (BioRad Kit #166-2500EDU) Introduction: Overview: The goal of the lab is to determine if a food sample contains GMO’s. In the first week , you will extract genomic DNA from food samples and run polymerase chain reactions (PCR) to amplify GMO and natural plant sequences from the DNA. In the second week , you will separate and detect certain DNA sequences using gel electrophoresis as shown in Figure 1.
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2 Fig. 1. Detecting GM foods by PCR. Genomic DNA is extracted from test foods and then two PCR reactions are performed on each test food genomic DNA sample. One PCR reaction uses primers specific to a common plant gene (plant primers) to verify that viable DNA was successfully extracted from the food. No matter whether the food is GM or not, this PCR reaction should always amplify DNA (See lanes 1 and 3 of the gel above). The other PCR reaction uses primers specific to sequences commonly found in GM crops (GMO primers). This PCR reaction will only amplify DNA if the test food is GM (See lane 4). If the test food is non-GM, then the GMO primers will not be complementary to any sequence within the test food genomic DNA and will not anneal, so no DNA will be amplified (see lane 2). To find out whether DNA has been amplified or not, the PCR products are electrophoresed on a gel and stained to visualize DNA as bands. A molecular weight ruler (lane 5) is electrophoresed with the samples to allow the sizes of the DNA bands to be determined. Electrophoresis (Used for Week 2) Gel electrophoresis using a polyacrylamide gel is the method used to separate different size DNA fragments. In general, electrophoresis is the movement of ions in an electric field. This technique is an extraordinarily important method of separating and analyzing biological molecules. The movement of a molecule in an electric field E is a function of net charge q and the frictional coefficient f . The velocity v at which a molecule moves in an electric field is a function of the field strength and net charge as defined by the relationship given below. f Eq = ν A molecule’s mobility μ is defined as the ratio of velocity to field strength. By extension, mobility is also equal to the ratio of charge and frictional coefficient as illustrated below: f q E = = The frictional coefficient is a measure of the hydrodynamic size of the molecule wherein the larger the molecular size of a molecule, the larger the frictional coefficient. Molecular shape is also an important component of the frictional coefficient. Biological molecules like proteins and polynucleic acids have distinctive shapes. Therefore, the electrophoretic mobility of a biological macromolecule is a function of its size, shape, and net charge.
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3 Week 2: Gel Electrophoresis, Staining, and Analysis In lab last week, DNA was extracted from non-GMO (Genetically Modified Organism) and test food samples as well as positive control GMO DNA. The DNA was then amplified using the polymerase
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This note was uploaded on 07/02/2011 for the course CHEM-C 118 taught by Professor Flood during the Spring '10 term at Indiana.

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GeneticallyModifiedFoodsWeek2 - C118 Laboratory -...

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