Crime Scene Investigation

The field of DNA profiling is relatively new, however, it is already being applied with great success by law enforcement. Using restriction enzymes to "cut" the DNA at certain points different sized strands of DNA are produced. This is called Restriction Fragment Length Polymorphism. Restriction enzymes are a naturally occurring bacterial defense system. They destroy invasive DNA by cutting it into small parts that will be harmless to the host. Using this technique allows the strands to be separated. Once separated the nucleotide sequence will be checked for similarities to suspects DNA nucleotide sequences. Any biological material that is found at a crime scene can be tested in this fashion and compared to suspects DNA in an attempt to solve a crime. Once the strands are separated they are placed on an agarose gel and electrified. The DNA has a negative charge so it will move towards the positive pole of the gel. The DNA can then be checked against suspects DNA to determine the perpetrator.

First, we removed the DNA samples and placed them in a centrifuge. Then we added 5 microliters of loading dye, which makes the DNA and also makes the sample heavier. Then we loaded the DNA samples into the wells in the agarose gel. Then we turned on the power to separate the samples with electricity. Then we waited 2 days and then placed the gel on a white box to examine the samples.

We concluded that suspect 3, Chloe, was the murderer. We saw that the DNA marks in her track matched the ones of the DNA that was found at the crime scene. These markings were fairly straightforward and easy to read. However, we could have possibly contaminated samples by using the same pipette tip or placing DNA in the wrong well.