DNA Fingerprinting in Forensics |
What is a scientist doing an electrophoresis on DNA from a crime scene looking for in the test results? If the suspect's DNA and the evidence DNA have similar patterns of bands after being cut with restriction enzymes and run through an electrophoresis gel, it means the sample may have come from the same person. Click here to get a more detailed explanation by selecting each topic in the index successively. |
What evidence can a person leave behind that can be examined for a DNA match? Hair, blood, skin, saliva, semen...these all make good sources of DNA information. To run a hair sample match several hairs are needed and must have been pulled from the scalp including the follicle. In any case, no matter how small the sample of DNA collected it can be amplified by using a PCR reaction. |
Click on the PCR denaturation graphic below to uncover the series of steps needed to increase the number of DNA molecules present in a sample. |
Here is a set of gel samples matched to the ladder at the left. The ladder identifies the number of base pairs producing the band at that specific location in the gel. The darker the gel, the more fragments of that particular size. |
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Looking at the samples above, which would you say seemed most like each other? Why? Which seem to be least like any other? Why? |
Sometimes, radioactive labels are used to make bands more pronounced. |
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Look at the samples in lanes 4,5,7,11, and 12. How are they different from the other lanes? How are they like each other? What is the significance of lane 8? |
