DNA profiling.

We are finishing genetics in our Biology lessons, and one of the main experiments we performed was DNA profiling. For this experiment, we used gel electrophoresis. An important step before we start is to put gloves on, so we don’t put any pieces of our own DNA into the sample and contaminate the results.

We placed four identical copies of the same DNA strand into four containers. The first container was empty, but the other three had different restriction enzymes. Each of this restriction enzymes cut the DNA strand after different sequences. These enzymes were EcoRl, BamHl sonf HindIII.

After placing the DNA in the different containers, we placed the containers into a hot water bath (About 36º C but I’m not completely sure) for the enzyme to work correctly and a bit faster. while we wait for the enzyme to cut the entire pieces of DNA, we poured agarose gel into the electrophoresis tank and and let it there a couple of minutes so it solidifies.

While the gel in the electrophoresis tank is solidifying, we mixed the samples (each of them separately) with ink. When the gel is solidified we placed two carbon fibre tissues on each side of the electrophoresis tank. Then we put some TBE buffer on top of it. After that we pour the samples of DNA already mixed with the ink carefully into the wholes of the gel with a micro syringe through the buffer. 

As the DNA is negatively charged, it would be attracted to a positive pole of electricity, but it would be more difficult to attract the big strands of DNA than the smaller ones so if we let the magnets attract the different samples through the gel for a couple of hours, we will be able to appreciate different strands of DNA placed through the gel, the ones that are nearer to the opposite site of the tank would have to be smaller and the ones that are nearer to the other site of the tank should be bigger. by doing this, we can compare the result to another sample and get conclusions like if they are the same person or even if they are related. 

For doing this, we connected two wires to each site of the tank, attaching them to the carbon fibre, creating therefore an electric attraction that is able to move the gel. After being connected for two hours, we disconnect the electricity and analyze the results in the gel.

(Photo credits: Oliver Ferres)