Crime Lab Simulation: DNA Analysis with Agarose Gell Electrophoresis

SWBIC Educational Resources  >> Activities & Materials  >> DNA Fingerprinting  >> Scenario

As part of your training as a BIODETECTIVE, you will participate in a crime lab simulation. You must use your skills and knowledge to figure out who has committed the crime. It is important that you pay close attention to details in this activity since the results of your investigation will play a key role on whether one of the suspects should walk free or be sent to jail.

It’s been two days since this hideous crime was committed. Mary Gozalez, a sweet and active senior citizen in the community, was coming back home after shopping. When she entered her house, she noticed that something was not quite right. The window to the kitchen was wide open. As she walked toward the window she was pushed by man a wearing a ski mask. Luckily, Mary was not hurt as the man only pushed her against the wall as he ran out of the house. Mary immediately called the police, and your team was assigned to the case. You discovered that all of Mary’s valuables (jewelry, cash, and a very expensive antique replica of the David was taken). The thief was obviously a professional because he took good care of no leaving any fingerprints or any other obvious clues in the house. We only know that he was about 6.0 ft tall and that he most probably was a man because of his body shape.

Just when you were about to give up on this case, one of your team members came up with a great idea. Maybe the assailant left a clue on Mary’s dress when he pushed her aside. You asked Mary for the same dress she was wearing that day, and there you finally found some possible clues–strands of hair on Mary’s dress. After conducting a variety of DNA and simple tests, you were able to determine that some of the hair came from Mary herself, some belonged to her neighbor’s cat, and some belonged to the owner of the grocery store. However, you found one single and short strand of hair on her dress that did not seem to match anyone she knew. “This may be it!!” you thought. You managed to round up two suspects and now you have a chance to see if the hair you found belongs to one of them. One of the suspects is Alfred, a US African male who lives a few blocks from Mary. He was seen walking in front of Mary’s shortly after she called the police. Alfred claims that he always walks by that house on his way home from work. The other suspect is Peter, an Anglo male who delivers milk in the neighborhood. He has been seen walking around the houses as if looking for something. He claims that he only walks around the house when he needs to collect payment and no one answers the door.

Based on the clues so far, make a prediction: Who do you think is the most likely person to have committed the crime? Why? Explain your answer below.

After you complete the analysis of your sample, can you be 100% sure of who committed the crime? Why? What kind of errors or situations could interfere with arriving at the correct decision?

Next. . .follow the procedures in the attached pages to conduct the DNA analysis. . .In the space below, write down who you think committed the crime.


Procedure for DNA Analysis