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This lab is about using gel electrophoresis to compare the DNA samples of 4 suspects to DNA found at a crime scene. Gel Electrophoresis sorts DNA by length or charge. 6 viles of DNA have been put through PCR will have restriction enzymes mixed in. A Jell-O like substance from Argose and a liquid buffer is combined and placed in a mold with a gel comb making little wells, then refrigerated until it is formed into a gel. The gel is placed in a container, slightly submerged in a liquid buffer. In our case, the liquid buffer was water.
We put the viles in ice for an incubation period so that the DNA would not expire, and prepared to insert them into the gel. We then inserted a 15 microliter sample of each DNA vile into our gel including our crime scene DNA, so that we had something to compare our results to. After this, an electric charge is turned on, positive on the side of the wells, negative of the opposite side of the container. Since DNA is negatively charged, and opposites attract, the DNA moves through the gel towards the positive charge. The short, thin strands of DNA will get closer to the positively charged buffer rather than the long, fat strands because they can maneuver through the gel more easily due to their small size.
Advances in biology over the past several years can be credited to our ability to now manipulate DNA. A primary tool that is used for recombinant DNA technology are enzymes, which cut, mend, wind, unwind, transcribe, repress, and replicate DNA. What are known as restriction enzymes allow us to cut DNA at specific nucleotide sequences. Restriction enzymes are able to scan along a length of DNA looking for a particular sequence of bases that they recognize. A sample of DNA, incubated with restriction enzymes, results in millions of varying sizes of DNA fragments. These fragments are separated by running an electrical current in agarose gel electrophoresis, and stained with a color for easy observation.
The purpose of this lab is to find which of the five samples of suspect DNA is identical to that of the DNA found from the crime scene. With the use of restriction enzymes, we will be able to cut similar segments of each sample of DNA. By running them through gel electrophoresis, we can match the gel’s visual representation of each sample’s segment length and determine which sample corresponds to that of the sample found at the crime scene.
If we run the samples through gel electrophoresis, then we can find which suspect DNA sample matches the one found at the crime scene because gel electrophoresis separates segments shared between each DNA sample and shows how long each one is. If the lengths of any segment match, then we will know that the DNA is the same.