Lab 18 DNA Murder Mystery

Lab 18DNA Murder

MysteryBY-102

Zach Nolen

DNA Fingerprinting

0 Is a technique used by forensic scientists to identify people based on their DNA profiles

0The key to DNA fingerprinting is Restriction Fragment Length Polymorphisms (RFLPs)

When is it used?

0Crime Investigations0 Rape0 Violent Crimes

0Familial Relationships0 Paternity tests

How Specific Are RFLPs?

0Under normal circumstances, no other human has your exact complement of genes, unless…

0You 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

0Richard Buckland (17 years old)0 Local with learning disabilities0 Worked at Carlton Hayes psychiatric hospital0 Seen near murder scene of Dawn Ashworth0 Knew detailed information regarding body of deceased0 Confessed to the murder of Dawn Ashworth but not to

the murder of Lynda Mann

Suspect 2

0Colin Pitchfork (27 years old)0 Local baker0 Previous convictions for flashing0 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

1. Extract DNA2. Amplify DNA3. Cut DNA4. Sort DNA5. Denature DNA6. Hybridize DNA7. Make an X-Ray

Extract DNA

0We performed an extraction last week using cold ethanol. Keep in mind that there are other ways to extract DNA.

0We will be going through these steps using the DNA sheet that you should have printed out.

0 If you do not have the sheet, I have a few extras.

Amplify DNA

0We amplify DNA using Polymerase Chain Reaction (PCR).

0This allows us to increase the total amount of DNA that we have

0For our exercise, everyone having their copy of DNA will act as the amplification

Cut DNA0To cut DNA, Restriction enzymes are used.0These enzymes cut DNA by recognizing specific sites in

chains of DNA0We will act as restriction enzymes and cut our DNA at the

indicated sites.0 Make sure that the sites match exactly

NeoSci 15’ GG|CC 3’ 3’ CC|GG 5’

NeoSci 25’ GA|AG 3’3’ CT|TC 5’

Sort DNA

0After the DNA is cut using restriction enzymes, it must be sorted using gel electrophoresis

0This process separates DNA fragments based on size0We will cut paper DNA fragments out ant place them

on our paper gel0Fill out p. 215 by placing dark lines at any location

where a fragment would be present

Denature DNA

0After the DNA has been sorted, it must then be denatured using either heat or chemical.

0To denature our DNA, we will remove the yellow strips from the bottom of the fragments in our lanes

Hybridize DNA

0This step binds a radioactive probe to the fragmented DNA so that it can be seen.

0We will cut out the “T C C” probes and place them under fragments with the corresponding letters “A G G”

Make an X-Ray

0The process of taking an X-Ray of hybridized DNA is called Autoradiography

0Fill in lines on p. 214 to indicate fragments where hybridization has occurred.

Results

0Suspect 2: Colin Pitchfork is the murder.0Colin Pitchfork was the first person ever to convicted

of murder based on DNA fingerprinting evidence.

Paternity Tests

Review Questions

1. What is the key to DNA fingerprinting?2. What can DNA fingerprinting be used for?3. What do we use to cut DNA?4. How do we sort DNA?

Before you leave lab

0Clean up your work station

Before next lab

0Read Lab 7 – The Cardiovascular System0Do Online Prelab0Complete sections in lab manual for lab notebook

check