Is a unique to every person but the
same for the cell to cell within the
DNA cannot be altered*
– Actually DNA can be altered in the lab, but you can’t
change your own DNA
Two kinds of fingerprint
– Becoming the primary
method for identifying
among individual human
What is DNA
A technique used by scientists to
distinguish between individuals of the
same species using only samples of
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.
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.
DNA Fingerprinting Real
Forensic science is the use of
scientific knowledge in legal
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
Biological materials used
for DNA profiling
Body tissue cells
DNA samples have
been obtained from
transferred to the
outside of a condom
A DNA Fingerprint
When many genes are
analyzed, each with many
different alleles, the chance
that two patterns match by
coincidence is vanishingly
A DNA fingerprint used in a
The defendant stated that the
blood on his clothing was his.
What are we looking at? How
was it produced?
DNA Profiling can solve
The pattern of the DNA profile is then
compared with those of the victim and the
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
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:
Was the suspect at the
Colin Pitchfork was
the first criminal
caught based on
He was arrested in
1986 for the rape
and murder of two
girls and was
sentenced in 1988.
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 profiles can be used to determine
whether a particular person is the parent of
A childs paternity (father) and
maternity(mother) can be determined.
This information can be used in
• Paternity suits
• Inheritance cases
• Immigration cases
Example: A Paternity
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.
Is this man the father of
In general the child’s
DNA must be a
combination of Mary’s
DNA and one of the
men. Which man is the
DNA fingerprinting is used
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
(mother) (child 1) (child 2) (father)
In 2002 Elizabeth
Hurley used DNA
profiling to prove
that Steve Bing was
of her child Damien