Modern Biology provides 50 products for incorporating gel electrophoresis into laboratory exercises for high school and college biology students. Some of the most fascinating applications of gel electrophoresis for advanced high school and college biology students are plant physiology lab experiments.

Identifying GMO

Consider this question that is of interest to nearly every student: How can you tell whether a plant food is GMO or non-GMO?

Your students may have some creative answers to this question. But the way labs test for genetic modification is to look for the transcription terminator of the nopaline synthase (NOS) gene of a common species of bacteria that lives in the soil called Agrobacterium tumefaciens.

This extraordinarily useful bacterium has a natural ability to insert its DNA into a host plant. Genetic engineers use this ability to transfer genes of choice to transfer genes into genes to produce a GMO. When genes are transferred in this process, the bacterium’s nopaline synthase transcription terminator remains in the target plant’s genome. 

Exactly What is Being Tested For?

Every transcription terminator is a sequence of DNA. The NOS terminator is a 127 base-pair sequence of DNA that appears in 85 percent of genetically modified plants. 

In addition to their own DNA, plants contain organelles known as chloroplasts that contain different DNA sequences. Laboratories can extract DNA from chloroplasts to confirm that they are working with plant DNA, and not DNA from a bacterium.

In testing for genetic modification, there are two possible results. If the polymerase chain reaction works, then we should observe at least a band of chloroplast DNA and the control sequence after gel electrophoresis. If there has been a genetic modification, then there will also be a band corresponding to the NOS sequence of the inoculating bacterium.
Is genetic modification testing something your students can accomplish in a single, three-hour lab?

The simple fact is, your students will have to have become proficient in several lab skills to pull this off.

The Important Steps

The first step is the extraction of DNA from plant tissue. This step takes about 20 minutes but goes faster if your students have experience in cell fractionation and DNA extraction from either plant or animal tissues, such as Modern Biology’s B1-2: Cell Fractionation and DNA Isolation.

The second step is the amplification of both chloroplast and NOS DNA through PCR, the polymerase chain reaction. For many students, the challenge is pipette technique. They can master the manual skills they need for this part of the experiment with earlier exercises such as IND-07: Amplification of a Hemoglobin Gene by PCR. If they have, then most of their time will be spent waiting on PCR. This part of the experiment can take as long as two hours.

The final step of this kind of testing involves gel electrophoresis. Cast a gel, set a 100 base pair ladder, and run electrophoresis with a control with the results of your PCR. Then visualize the gel. Well-prepared students will need 40 minutes for the final part of this experiment.

Of course, you don’t have to be this ambitious with every class. You can use Modern Biology to build the skills students need to find the laboratory answers to the questions that are of interest to them.

Every experiment kit from Modern Biology contains everything your students will need for a hands-on exercise in scientific thinking. Your students will develop the lab skills they need to succeed in future courses, and you will have everything you need for teaching the lab all in one place.
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