1. A technique used by scientists to distinguish between individuals of the same species using only samples of their DNA DNA Profiling (DNA fingerprinting) Who Invented it? Alec Jeffreys at the University of Leicester in 1985. He was knighted in 1994.

2. Where do you get the DNA? All cells in our body have DNA, but the riches sources of DNA that are best for evidence are found in ….. • Blood • Hair • Saliva • Semen or vaginal fluid • Body tissue cells

3. chromosome cell nucleus Double stranded DNA molecule Target Region for PCR Individual nucleotides DNA in the Cell

4. Stages of DNA Profiling • Stage 1: Cells have to be broken down to release DNA If only a small amount of DNA is available it can be amplified using the polymerase chain reaction (PCR)

5. Add chemicals so the DNA is forced to precipitate out of solution…. • It is white and gooey and can be pulled out by twisting a rod around it

6. 4 base pairs attract each other to zip up the double helix. • Everyones genes have different combos of these 4 pairs

7. Stages of DNA Profiling • Step 2: add more chemicals The DNA is cut into fragments using restriction enzymes. Each restriction enzyme cuts DNA at a specific base sequence. This means everyone’s unique DNA is cut into different size peices.

8. Stages of DNA Profiling • The sections of DNA that are cut out are called restriction fragments. • This yields thousands of restriction fragments of all different sizes because the base sequences being cut may be far apart (long fragment) or close together (short fragment).

9. Stages of DNA Profiling Stage 3: • Fragments are separated on the basis of size using a process called gel electrophoresis. • DNA fragments are injected into wells and an electric current is applied along the gel.

10. Stages of DNA Profiling DNA is negatively charged so it is attracted to the positive end of the gel. The shorter DNA fragments move faster than the longer fragments. DNA is separated on basis of size.

11. Stages of DNA Profiling • A radioactive material is added which combines with the DNA fragments to produce a fluorescent image. • A photographic copy of the DNA bands is obtained.

12. Load gels with crime scene DNA samples alongside 2 suspects to see whose DNA fragments match 6 5 4 3 2 1 Suspect 2 DNA 1 Suspect 1 DNA 2

13. Compare to other students results. Are they all consistent?

14. Gel Electrophoresis of DNAUse these photos in your lab report 6 5 4 3 2 1

15. Load gels with crime scene DNA samples alongside 2 suspects to see whose DNA fragments match Suspect 2 DNA 1 Suspect 1 DNA 2

16. Load gels with crime scene DNA samples alongside 2 suspects to see whose DNA fragments maych