Lab 18 DNA Murder Mystery BY-102 Zach Nolen

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)

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

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

Murder Case

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.

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

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.

How can we find the culprit? DNA Fingerprinting

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

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.

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

Cut DNA NeoSci 1 5’ GG|CC 3’ 3’ CC|GG 5’ NeoSci 2 5’ GA|AG 3’ 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’

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

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

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”

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.

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

Paternity Tests

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?

Before you leave lab Clean up your work station

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