LO:
DNA Profiling
5 Describe how DNA profiling is used for identification and determining
genetic relationships between organisms (plants and animals).
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DNA profiling is a technique that allows an individual’s genes to
be visualised. This allows someone's genetic makeup to be
compared to known genes to see if they too have them.
This technique can be used to identify
genetic disorders in individuals or match
DNA samples to individuals.
We usually sample regions of DNA called
introns, once called Junk DNA, since it
varies between individuals (but not
twins). As opposed to exons (genes in
the normal sense). These repetitive
regions of ‘Junk DNA’ are now called
STRs: Short Tandem Repeats.
Alex Jeffreys’ first use of DNA Profiling: http://www.youtube.com/watch?v=Fz6p8EgJZ3w
Sources of DNA for Genetic Profiling
How do we get the STRs from the DNA sample?
You’ll need to macerate the sample and
add enzymes to break down the
cellular membranes.
We’ll need to cut out the sequences of DNA we wish to compare, the STRs.
Enzymes are perfect for this, specifically restriction enzymes (restriction
endonucleases) which cut at designated DNA sequences.
Samples must be compared against possible sources
Suspects
Profile
Blood
sample from
crime scene
Victims
profile
Is this man the father of the child?
Mother
Child
Man
Famous Cases
• Colin Pitchfork was
arrested (1987) for the rape
and murder of two girls in
1986. He was only caught,
and then sentenced, in
1988 after DNA evidence
came to light.
Famous Cases
• In 1994 O.J Simpson was
cleared of murder charges
which relied heavily on DNA
evidence.
• The new technology, and the
jury’s lack of confidence with
it, formed a major part of the
case.
• This was later parodied in
SouthPark as the
Chewbacca Defence – it has
become a technical term.
https://www.youtube.com/watch?v=clKi92j6eLE
Old and modern forms of
gene profile presentation.