DNA fingerprinting was developed in 1984 by Alec J. Jeffrey at the University of Leicester. It involves analyzing variable number tandem repeats (VNTRs) in DNA to generate a unique profile for identifying individuals. DNA fingerprinting has six main steps: isolating DNA, cutting it with restriction enzymes, transferring fragments to nylon, probing with radioactive markers, and comparing the final fingerprint to other samples. This technique can solve crimes by matching DNA from a crime scene to suspects, determine paternity in inheritance cases, and has been used in famous cases like those involving Elizabeth Hurley and OJ Simpson.

1. (DNA fingerprinting)

2. Historical background
DNA fingerprinting was developed in 1984
by Alec. J. Jeffrey at the University of Leicester
He was studying the gene of myoglobin.
This is a picture of Alec. J. Jeffrey

3. What is DNA Fingerprinting?
The chemical structure of everyone's DNA is the same.
The only difference between people (or any animal) is
the order of the base pairs.
The information contained in DNA is determined
primarily by the sequence of letters along the zipper.
Structure of DNA

4. The different sequence
segments that
vary in size and
composition
and have no
apparent
function are
called
minisatellites
The different sequences is the same as the word "POST"
has a different meaning from "STOP" or "POTS," even
though they use the same letters. i

5. Using these sequences, every person could be identified
solely by the sequence of their base pairs
 there are so many millions of base pairs, the task would
be very time-consuming
Instead, scientists are able to use a shorter method,
because of repeating patterns in DNA.
These patterns do not, however, give an individual
"fingerprint,"
they are able to determine whether two DNA samples
are from the same person, related people, or non-
related people.

6. DNA Fingerprinting using
VNTR'sOn some human chromosomes, a short sequence of
DNA has been repeated a number of times.
 the repeat number may vary from one to thirty repeats
these repeat regions are usually bounded by specific
restriction enzyme sites
cut out the segment of the chromosome containing this
variable number of tandem repeats (VNTR's )
identify the VNTR's for the DNA sequence of the
repeat.

7. Making DNA Fingerprints
DNA fingerprinting is a laboratory procedure that requires
six steps:
1: Isolation of DNA.
2: Cutting, sizing, and sorting.
Special enzymes called restriction enzymes are used to cut
the DNA at specific places

8. 3: Transfer of DNA to nylon.
The distribution of DNA pieces
is transferred to a nylon sheet
by placing the sheet on the gel
and soaking them overnight.
4-5: Probing.
Adding radioactive or colored probes to the nylon sheet
produces a pattern called the DNA fingerprint.

9. 4-6: DNA fingerprint.
The final DNA fingerprint is built by using several
probes (5-10 or more) simultaneously.

10. Stages of DNA Profiling
Stage 1:
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)

11. 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.

12. 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).

13. 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.

14. 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.

15. 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.

16. 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).

17. 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.

18. 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.

19. 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:

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

21. 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
• Immigration cases

22. 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.

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

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

25. Famous Cases
O.J. Simpson was
cleared of a double
murder charge in 1994
which relied heavily on
DNA evidence.
This case highlighted
lab difficulties.

26. DNA fingerprinting