DNA Fingerprinting

Television makes DNA fingerprinting seem fast and easy. The truth is that it takes quite a bit of time and requires very careful controls and verification. For these reasons, and due to a backlog of cases, DNA results can take weeks to months to come back from the lab. Television, of course, gives you the results in 5 minutes confused.

Follow the instructions below to learn how scientists match DNA.

1. Go to this site and watch the animation on the Southern Blot technique.

2. For more details on what goes on inside the gel, go to this site. Be sure to click the 'Can DNA Demand a Verdict' link after you finish the interactive and read more about how gel electrophoresis is used in forensic investigations.

3. Next, go to this site to run a virtual lab and catch a candy thief! Click on the 'view' button to start the activity.

4. Then go to this site and read the tutorial on the process. Click on the DNA Forensics Problems button at the bottom of the tutorial and complete the problem set (6 problems).

5. It turns out that forensic scientists have switched from analyzing VNTRs (variable number tandem repeats) to analyzing STRs (short tandem repeats). The overall idea for catching a criminal is the same but the use of STRs is more efficient. Read this page to read about the difference between VNTRs and STRs and see why they switched. This page also has a quick blurb to describe the difference and its advantage.

6. Finally, go to this site and complete the karyotyping activities for the three cases. While karyotyping is not the same thing as DNA fingerprinting - it is still a good thing to know :-)

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