Crime Scene Investigation (Adopted from Forensics in the Classroom developed by Court TV)

Transcription

1 Crime Scene Investigation (Adopted from Forensics in the Classroom developed by Court TV) The case: Last night, the school cafeteria was vandalized; the kitchen area was broken into, several appliances were damaged, the gas line was cut, and the pantry was ransacked. No personal injuries occurred. The crime was first noted this morning by the kitchen staff when they arrive for work early in the morning. After careful inspection of the crime scene and a lot of follow up inquiries into it; the team in charge of the investigation has been able to establish the following leads and hope to wrap up the case very soon. The leads & facts in the case: There are five suspects that all members of a gang, which is believed to be responsible for this and another incident in the neighborhood that occurred last night too; all part of an initiation ritual. All gang members are related by blood, that is, they are members of the same family. Fresh blood was found near the area where the gas line was cut; since the kitchen is scrub clean every day before closing by the kitchen staff; it is then presumed that the blood is a strong piece of evidence AND that it belongs to the person that cut the gas line. An initial search of the databases at the crime scene lab with the evidence blood does not yield any match. Therefore, blood samples have been requested and obtained from each one of the five suspects. The crime scene lab run several tests on all the blood samples and these are the findings that seem significant: Evidence Suspect1 Suspect2 Suspect3 Suspect4 Suspect5 Blood A A A A A A type Hepatitis Positive Positive Positive Negative Negative Negative From the results, two suspects emerged as the most likely culprits, Suspect1 and Suspect2. Now, the police requests your help to be able to issue an arrest in this case. What you need to know before proceeding: Hepatitis is a disease that is caused by a virus; however, there are many types of hepatitis, many different types of viruses that can produce the disease, and within a particular strain of the virus, there could be several mutations. Hepatitis A, PDB ID:1hav hepatitis B, PDB ID:1qgt hepatitis C, PDB ID: 1a1q These are the protein structures of three different types of hepatitis-causing viruses; they were retrieved from the PDB (Protein Data Bank) you can also do it by typing the PDB ID of each structure.

2 However, we cannot obtain the protein structure of the hepatitis virus directly from the blood samples. What the crime scene lab has been able to produce on short notice- is the amino acid sequence of the hepatitis virus contained in each blood sample. a) We ask you to compare the strain of the hepatitis virus found in each one of the three blood samples to see if there is a match >sample1_evidence >sample2_suspect 1 >sample3_suspect 2 b) Following are the amino acid sequences of each one of the protein structures in the above figures. Try matching the specific type of hepatitis present in each blood sample to one of sequences below. >PDBFINDER:1HAV_A Hepatitis_A Virus >PDBFINDER:1QGT_B Hepatitis_B Virus STL >PDBFINDER:1A1Q_B Hepatits_C Virus APITAYSQQTRGLLGCIITSLTGRDKNQVEGEVQVVSTATQSFLATCVNGVCWTVYHGAGSKTLAGPKGP ITQMYTNVDQDLVGWQAPPGARSLTPCTCGSSDLYLVTRHADVIPVRRRGDSRGSLLSPRPVSYLKGSSG GPLLCPSGHAVGIFRAAVCTRGVAKAVDFVPVESMETTMRSPVFTDNSS Present your findings to the investigative team Is there a match between the evidence blood and any of the samples coming from the suspects? Which type of hepatitis is present in the match? Are your findings conclusive? please explain NOW TRY DOING IT THE EASY WAY: WITH THE BIOLOGY STUDENT WORKBENCH!

3 ANSWER SHEET a) Comparing the evidence blood sample against the suspects blood sample >sample1_evidence >sample2_suspect 1 >sample3_suspect 2 Evidence blood sample / Suspect 1 blood sample. Match? NO Evidence blood sample / Suspect 2 blood sample. Match? YES b) Comparing blood samples against hepatitis virus sequence >PDBFINDER:1HAV_A Hepatitis_A Virus >PDBFINDER:1QGT_B Hepatitis_B Virus >PDBFINDER:1A1Q_B Hepatitis_C Virus Evidence blood sample, type of hepatitis virus: Hepatitis B virus Suspect 1 blood sample, type of hepatitis virus: Hepatitis A virus Suspect 2 blood sample, type of hepatitis virus: Hepatitis B virus

4 ANSWER SHEET: WITH THE BIOLOGY STUDENT WORKBENCH! 1. Go to the Biology student workbench website at 2. Click on Use Student Workbench 3. To enter the workbench type userid: beckman_oh password: user 4. Select the session name: CSI located at the bottom of the screen click on Resume to go to that session 5. Let s compare the evidence against the blood samples from the suspects. click on Protein Tools. Then scroll to the bottom of the screen and select TWO sequences at a time for the comparisons: sample1_evidence sample2_suspect1 then click on ClustalW located inside the box, ClustalW is a tool that will align two or more sequences Look at the results displayed on the screen. Is it a match? i.e. do the two sequences align almost 100%? click on Return and repeat the same process with sample1_evidence sample3_suspect2. Did you find a match between these two sequences? 6. Now let s find out which type of hepatitis each sample contains Make sure are back on the screen that reads Student Interface to the Biology Workbench. Scroll to the botton of the screen and select All three hepatitis sequences AND the evidence sample; that is four sequences in total. Now click on ClustalW to align them all at once. Notice that by aligning them all and choosing the one sequence that aligns best with the evidence sample, we are answering the question of which one of the sequences is the most similar to the evidence sample. Look at the results displayed on the screen. Which type of hepatitis is the most similar to the evidence? Let s see the results in a phylogenetic tree. Remember, in that type of tree, similar sequences end up closer together in the same part of the tree. While still on the screen that shows the ClustalW results, click on Import Alignment then, you are taken to a different screen, scroll down and select the alignment that ClustalW produced, then click on DRAWTREE Locate the branch of the tree that has the evidence sample and look for its closest neighbor. That s it!

5 Is there a match for evidence blood? which type of hepatitis did it match to? Repeat the same steps with the other two samples and write down the answers Is there a match for Suspect 1 s blood? which type of hepatitis did it match to? Is there a match for Suspect 2 s blood? which type of hepatitis did it match to?