2. DNA
Is a unique to every person but the
same for the cell to cell within the
same person.
DNA cannot be altered*
– Actually DNA can be altered in the lab, but you can’t
change your own DNA
3. Two kinds of fingerprint
Conventional fingerprint
DNA fingerprint
– Becoming the primary
method for identifying
and
distinguishing
among individual human
being
4. What is DNA
Fingerprinting?
A technique used by scientists to
distinguish between individuals of the
same species using only samples of
their DNA
5. Who Invented it?
The process of DNA
fingerprinting was invented by
Alec Jeffreys at the University
of Leicester in 1985.
He was knighted in 1994.
6. DNA Fingerprinting Basics
Different individuals carry different alleles.
Most alleles useful for DNA fingerprinting differ on the basis of
the number of repetitive DNA sequences they contain.
8. 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).
9. 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.
10. A DNA Fingerprint
When many genes are
analyzed, each with many
different alleles, the chance
that two patterns match by
coincidence is vanishingly
small.
A DNA fingerprint used in a
murder case.
The defendant stated that the
blood on his clothing was his.
What are we looking at? How
was it produced?
11. 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.
12. 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:
13. Was the suspect at the
crime scene?
Suspects
Profile
Blood sample
from crime
scene
Victims
profile
14. 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.
15. Altantuyaa
Malaysian police found fragments of bone, later
verified as hers, in forested land near the Subang
Dam in Puncak Alam, Shah Alam. Police investigation
of her remains revealed that she was shot twice
before C-4 explosives were used on her remains,
although there has been later suggestion that the C-4
explosives may have killed her. When her remains
were found their identity could only be confirmed with
DNA testing.
16. 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
17. 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.
18. Is this man the father of
the child?
Mother
Child
Man
19. Paternity Test
In general the child’s
DNA must be a
combination of Mary’s
DNA and one of the
men. Which man is the
father?
Answer: Larry
20. DNA fingerprinting is used
for identification.
DNA fingerprinting depends
on the probability of a match.
– Many people have the same
number of repeats in a certain
region of DNA.
– The probability that two people
share identical numbers of
repeats in several locations is
very small.
(mother) (child 1) (child 2) (father)
21. Famous cases
In 2002 Elizabeth
Hurley used DNA
profiling to prove
that Steve Bing was
the father
of her child Damien
