Lab 18 DNA Murder Mystery

1. Lab 18DNA Murder Mystery BY-102 Zach Nolen

2. DNA Fingerprinting • Is a technique used by forensic scientists to identify people based on their DNA profiles • The key to DNA fingerprinting is Restriction Fragment Length Polymorphisms (RFLPs)

3. When is it used? • Crime Investigations • Rape • Violent Crimes • Familial Relationships • Paternity tests

4. How Specific Are RFLPs? • Under normal circumstances, no other human has your exact complement of genes, unless… • You are an identical twin

5. Murder Case

6. Murder Case After going missing, Lynda Mann, a 15-year old schoolgirl was raped and murdered in the grounds of Carlton Hayes psychiatric hospital in Narborough, Leicestershire, in November 1983. Forensic examination of semen sample that it was a type found only in 10% of men, and was from someone with type A blood. However, the police did not find a suspect. In 1986, another 150year old schoolgirl, Dawn Ashworth, was similarly sexually assaulted and strangled in the nearby village of Enderby, and semen samples showed the same blood type.

7. Suspect 1 • Richard Buckland (17 years old) • Local with learning disabilities • Worked at Carlton Hayes psychiatric hospital • Seen near murder scene of Dawn Ashworth • Knew detailed information regarding body of deceased • Confessed to the murder of Dawn Ashworth but not to the murder of Lynda Mann

8. Suspect 2 • Colin Pitchfork (27 years old) • Local baker • Previous convictions for flashing • Paid someone to give a false semen sample to police during the investigation supposedly because of his prior convections.

9. How can we find the culprit? DNA Fingerprinting

10. Steps • Extract DNA • Amplify DNA • Cut DNA • Sort DNA • Denature DNA • Hybridize DNA • Make an X-Ray

11. Extract DNA • We performed an extraction last week using cold ethanol. Keep in mind that there are other ways to extract DNA. • We will be going through these steps using the DNA sheet that you should have printed out. • If you do not have the sheet, I have a few extras.

12. Amplify DNA • We amplify DNA using Polymerase Chain Reaction (PCR). • This allows us to increase the total amount of DNA that we have • For our exercise, everyone having their copy of DNA will act as the amplification

13. Cut DNA • To cut DNA, Restriction enzymes are used. • These enzymes cut DNA by recognizing specific sites in chains of DNA • We will act as restriction enzymes and cut our DNA at the indicated sites. • Make sure that the sites match exactly NeoSci 1 5’ GG|CC 3’ 3’ CC|GG 5’ NeoSci 2 5’ GA|AG 3’ 3’ CT|TC 5’

14. Sort DNA • After the DNA is cut using restriction enzymes, it must be sorted using gel electrophoresis • This process separates DNA fragments based on size • We will cut paper DNA fragments out ant place them on our paper gel • Fill out p. 215 by placing dark lines at any location where a fragment would be present

15. Denature DNA • After the DNA has been sorted, it must then be denatured using either heat or chemical. • To denature our DNA, we will remove the yellow strips from the bottom of the fragments in our lanes

16. Hybridize DNA • This step binds a radioactive probe to the fragmented DNA so that it can be seen. • We will cut out the “T C C” probes and place them under fragments with the corresponding letters “A G G”

17. Make an X-Ray • The process of taking an X-Ray of hybridized DNA is called Autoradiography • Fill in lines on p. 214 to indicate fragments where hybridization has occurred.

18. Results • Suspect 2: Colin Pitchfork is the murder. • Colin Pitchfork was the first person ever to convicted of murder based on DNA fingerprinting evidence.

19. Paternity Tests

20. Review Questions • What is the key to DNA fingerprinting? • What can DNA fingerprinting be used for? • What do we use to cut DNA? • How do we sort DNA?

21. Before you leave lab • Clean up your work station

22. Before next lab • Read Lab 7 – The Cardiovascular System • Do Online Prelab • Complete sections in lab manual for lab notebook check