1. DNA Profiling
(DNA fingerprinting)

2. A Handful of DNA
This hand contains a lot of DNA but we can’t see it.

3. The more closely we look at the hand,
the more details we can see.

4. Tiny building blocks called cells make up your skin, and every other part of you. Thousands of cells surround every hair growing out of your skin. The cells are in the light purple area at the base of the growing hair. To find the DNA, we have to look more closely at the skin cells.

5. Different kinds of cells make up different parts of your body
Different kinds of cells make up different parts of your body. You have fat cells, muscle cells, and skin cells. If you look closely you can see the dark-staining nucleus of these cells. The DNA is smaller still....

6. There is DNA in nearly all of your cells, held in a sack called a nucleus. A nucleus is like the brain of the cell. It is where the cell stores all of the information it needs.

7. If you made a little hole in the nucleus sack, you would see DNA peeking through. If you took away the outside of the nucleus, the DNA would spill out like spaghetti.

8. Deoxyribonucleic acid DNA
An instruction manual for life

9. What colour How long Curly or straight brown curly shiny
DNA has information about your hair:
What colour
How long
Curly or straight
brown
curly
shiny

10. But also…. blue eyes blonde Your eye colour Height Shoe size
Skin colour
Freckles
Need glasses
Personality traits
Who your parents are
blue eyes
blonde
1.70 m tall

11. DNA contains lots of information about you
Everyone has information about the same things
So everyone’s DNA is different, just like your fingerprints are different from others
Scientists have found ways to compare people’s DNA

12. What is DNA Profiling?
A technique used by scientists to distinguish between individuals of the same species using only samples of their DNA

13. Stages of DNA Profiling
Cells are broken down
to release DNA
If only a small amount of DNA is available it can be amplified using the polymerase chain reaction (PCR)

14. Stages of DNA Profiling
Step 2:
The DNA is cut into fragments using restriction enzymes.
Each restriction enzyme cuts DNA at a specific base sequence.

15. 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).

16. Stages of DNA Profiling
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.

17. 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.

18. DNA negatively charged

19. 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.

20. Stages of DNA Profiling
The pattern of fragment distribution is then analysed.

21. Make up the gel which the DNA will be put into

24. Dye added to the DNA

25. Buffer solution added to the tank

26. DNA samples loaded into wells

27. Electrical current applied to the chamber

28. DNA is stained using ethidium bromide

29. Fingerprinting in the News
“Baby 81,” the 81st baby
brought to the hospital
after the tsunami in Sri
Lanka
The baby’s parents could not be identified for seven weeks
Nine mothers claimed the baby was theirs
DNA testing identified the true parents.

31. Uses of DNA Profiling
DNA profiling is used to solve crimes and medical problems

32. Crime
Forensic science is the use of scientific knowledge in legal situations.
The DNA profile of each individual is highly specific.
The chances of two people having exactly the same DNA profile is 30,000 million to 1 (except for identical twins).

33. Biological materials used for DNA profiling
Blood
Hair
Saliva
Semen
Body tissue cells
DNA samples have been obtained from vaginal cells transferred to the outside of a condom during sexual intercourse.

34. DNA Profiling can solve crimes
The pattern of the DNA profile is then compared with those of the victim and the suspect.
If the profile matches the suspect it provides strong evidence that the suspect was present at the crime scene (NB:it does not prove they committed the crime).
If the profile doesn’t match the suspect then that suspect may be eliminated from the enquiry.

35. Example A violent murder occurred.
The forensics team retrieved a blood sample from the crime scene.
They prepared DNA profiles of the blood sample, the victim and a suspect as follows:

36. Was the suspect at the crime scene?
Suspects Profile
Blood sample from crime scene
Victims profile

37. Solving Medical Problems
DNA profiles can be used to determine whether a particular person is the parent of a child.
A childs paternity (father) and maternity(mother) can be determined.
This information can be used in
Paternity suits
Inheritance cases

38. Example: A Paternity Test
By comparing the DNA profile of a
mother and her child it is possible to
identify DNA fragments in the child
which are absent from the mother and
must therefore have been inherited
from the biological father.

39. Is this man the father of the child?
Mother
Child
Man

40. Famous cases
In 2002 Elizabeth Hurley used DNA profiling to prove that Steve Bing was the father
of her child Damien

41. Famous Cases
Colin Pitchfork was the first criminal caught based on DNA fingerprinting evidence.
He was arrested in 1986 for the rape and murder of two girls and was sentenced in 1988.