DNA Fingerprinting

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DNA Fingerprinting
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DNA Fingerprint
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Step One

• Collect the sample!
• What do you think are the most common sources of
  DNA samples for forensic scientists?

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Step Two

• Extract and purify the DNA.
• Much the same as what we did with the Strawberry!!

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Step Three

• Cut the DNA!
• What do we use the cut DNA molecules?

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Step Four

• Sort the DNA by length!
• Big pieces slow
• Small pieces fast

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Sort by Length

• DNA has a negative charge.
• Electrophoresis machine has a positively charged
  probe on one end.

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Step 5

• DNA is split and transferred to a nylon sheet.
• A nylon sheet is blotted into the gel and DNA
  fragments are transferred onto it.

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Step 6

• Radioactive probes are attached to the DNA
  fragments.

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Lets practice!!!

• DNA strand AATCCGAATC
• DNA strand TACCGATTCG

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Step 7

• Nylon sheet with DNA fragments attached to
  radioactive markers is put into an x-ray machine.

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End Result!!!
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Step 8

• Analyze and compare results!

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Do we have a match?
blood stain
Bob
Sue
Juan
Lakisha
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Do we have a match?
blood stain
Bob
Sue
Juan
Lakisha