Genetically Modified Foods Lab Report

Purpose In this lab, we used PCR and gel electrophoresis to identify genetically modified food.

Introduction A genetically modified organism is an organism whose DNA or genetic makeup has been modified to code for certain desirable traits("Genetically Modified Foods"). Common genetically modified plants include corn and soy, and common genetically modified animals are fish. Many genetically modified plants are coded to resist bugs, grow faster, and produce bigger fruit, while most GMO animals are coded to grow faster and have better meat. This can help alleviate world hunger, and can also lower the cost of food production.(Calhoun) To determine if the food we selected was genetically modified, we used two biotechnology techniques: PCR and
gel electrophoresis. PCR stands for polymerase chain reaction, and it is used to make many copies of a specific piece or section of DNA ("PCR"). In PCR, primers and DNA polymerase enzyme is added to the extracted DNA of an organism. First, the temperature of the mixture is increased to 94 degrees Celsius, and the DNA unravels. This is the denaturation phase, and it lasts for 60 seconds. In the second phase, the temperature is lowered to 58 degrees Celsius and the primers match up with specific sections of DNA. This is called annealing, and it also lasts for 60 seconds. Lastly, in the extension phase, the temperature is increased again to 72 degrees Celsius, and the DNA polymerase makes copies of the sections of DNA with primers attached for 60 seconds. After 35 cycles of the process listed above, there is a large mass of copied sections of DNA. If there were two genes at the beginning of the first cycle, there will be two copies each of the two genes, or 4 sections total. At the end of the second cycle, there will be 8 sections of DNA total, and so on. Then, the DNA is loaded into an agarose gel to undergo gel electrophoresis. Gel electrophoresis is a laboratory method used to sort DNA fragments by size(Campbell, Williamson, & Heyden, 2004). In gel electrophoresis, the fragments to be separated move through an agarose gel that contains small pores. Because the pores in the gel are rather small, a small DNA molecule will travel a greater distance through the gel than will a larger DNA molecule("Gel Electrophoresis", 2014). As suggested by its name, gel electrophoresis involves electricity- one end of the gel has a positive charge and the other end has a negative charge. Because DNA and RNA are negatively charged molecules, they will be pulled toward the positively charged end of the gel, and bands representing fragments of different sizes can be seen.

Materials and Methods The positive control in our experiment was a prepared mixture of DNA fragments that were known to have genetically modified genes. The negative control was a prepared mixture of DNA fragments that were known not to have genetically modified genes. The independent variable was the type of food used to extract DNA from, and the dependent variable was whether or not the food was genetically modified. We used the materials and procedure detailed in the Edvo-Kit manual #962(Edvotek 9-17).
First, we extracted DNA from the selected food over the course of several days using a centrifuge and several micropipettes. At the end of the DNA extraction, there was a small pellet of DNA left at the bottom of the tube. We put this into a PCR tube, along with primers and DNA polymerase. We put the PCR tube into the PCR machine, where it underwent 35 cycles of denaturation, annealing, and extension. We then loaded the mass of copied DNA into a gel to undergo gel electrophoresis.

Conclusion The purpose of the lab was to use PCR and gel electrophoresis to identify genetically modified foods. This purpose was not achieved, because the gel results were inconclusive, and we could not determine if the foods we selected were genetically modified.
I was in Group 3 for this lab, and we used thin Oreos for our food.
At first, I thought that Oreos would not have plant cells in them and that we would not be able to extract DNA. However, I was surprised to see that there were bands on the gel. On the gel, there is one smear that is slightly lighter blue than its surroundings in the sixth lane. This smear is the plant chloroplast gene, which barely showed up on the positive control(Lane 2) and lanes 5 and 6. Lane 1 was the ladder, which showed DNA fragments of different sizes so we could compare. The third lane is the negative control, which was DNA that was known to not have genetically modified genes. The plant chloroplast gene showed up in this lane. However, it did not show up on the first group’s lane, and this was probably because they used soy sauce for their food. An experiment that we could conduct for further investigation is whether or not DNA can be extracted from soy sauce, and whether or not soy sauce is genetically modified. The smear in lane 6 shows that our group was able to successfully extract the DNA from the food, but it is unclear if there are any other bands besides the plant chloroplast gene. The plant chloroplast gene was 500 base pairs long, so it should have been the band on the top. The CaMV gene was 200 base pairs long, so it should have been further down the gel. The cry1F gene was 125 base pairs long so it should have traveled the farthest and been the farthest from the wells. We were able to see the plant chloroplast gene but no other bands can be
seen.
The inconclusive results may have been due to human error or limitations in equipment. There could have been several possible human errors during the course of the experiment. For example, maybe the DNA extraction was unsuccessful because the food did not have enough DNA, or because there was a pipetting error. Also, the PCR could have been unsuccessful because there was not enough DNA that taken out and put into the PCR tube, or the DNA may have been loaded into the gel incorrectly.
The equipment used to conduct the experiment was also limited. For example, the dye used to stain the gel so we could see the DNA bands was Amresco dye. Usually, the dye used to stain gels is called ethidium bromide, but this was a strong chemical, so we used a safer alternative. Although Amresco dye is safer than ethidium bromide, it does not stain the DNA as brightly or as clearly, so we were not able to see distinct bands. Also, the camera used to take pictures of the gel was not perfect. Usually, there are special cameras made to take pictures of gels, but we did not have that kind of camera available to us. As a result, the gel pictures were unclear.