DNA ProfilingLO:

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5 Describe how DNA profiling is used for identification and determining genetic relationships between organisms (plants and animals).

Alex Jeffreys’ first use of DNA Profiling: http://www.youtube.com/watch?v=Fz6p8EgJZ3w

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 it.

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 STR’s: Short Tandem Repeats.

Sources of DNA for Genetic Profiling

How do we get the STR’s from the DNA sample?

We’ll need to cut out the sequences of DNA we wish to compare, the STR’s. Enzymes are optimum for this.

Specifically restriction enzymes (restriction endonucleases) which cuts at specified DNA sequences.

You’ll need to macerate the sample and add enzymes to break down the cellular membranes.

Suspects Profile

Blood sample from crime scene

Victims profile

Samples must be compared against possible sources

Is this man the father of the child?

Mother Child Man

Famous Cases

• Colin Pitchfork, arrested in 1986 for the rape and murder of two girls. He was only caught in 1987 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.