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DNA Fingerprinting Simulation Step 1: Pour restriction enzymes into DNA
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What happens The restriction enzymes act like scissors that cut the DNA into smaller fragments Because each person has a unique DNA sequence, his or her DNA is cut in a unique pattern The lengths of the fragments will vary from person to person
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Step 2: Pour agarose gel into tray on lab counter
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What happens Agarose gel has a web-like molecular structure similar to that of Jell-O The agarose gel separates the DNA fragments based on size because larger fragments have a harder time moving through the “web” and move more slowly than smaller fragments
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Step 3: Pour DNA into tray
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What Happens? The DNA is added to depressions, or holes, in the agarose gel http://ocw.mit.edu/NR/rdonlyres/Biological-Engineering/20-109Fall- 2007/51DB7724-07DA-45ED-A3CE-7C06AA5C1963/0/mod1_2_agaro_gel.jpg http://ocw.mit.edu/NR/rdonlyres/Biological-Engineering/20-109Fall- 2007/381532A7-44EE-4E62-9F57- 83DEA4D0EFBA/0/mod1_2_photo.jpg
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Step 4: Turn on switch to begin electrophoresis
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What happens? The electric current causes the DNA molecules to begin moving DNA fragments have a slight negative charge, so they move toward the positive end of the gel/tray. By the end of electrophoresis the fragments will be separated according to their lengths.
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http://ocw.mit.edu/NR/rdonlyres/Biological-Engineering/20-109Fall-2007/381532A7-44EE- 4E62-9F57-83DEA4D0EFBA/0/mod1_2_photo.jpg
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Step 5: Place nylon membrane on top of the gel
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What happens? The agarose gel is very thin and difficult to move around, so a nylon membrane is placed on top of it The nylon membrane “blots” up the DNA (kind of like a paper towel)
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Step 6: Add probes to nylon membrane
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What happens? The radioactive probes attach themselves to DNA fragments that have stuck to the nylon membrane Any excess (non-stuck) probes are washed away
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Step 7: Place x-ray film on top of nylon membrane
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What happens? The radioactivity from the probes exposes the x-ray film in any places where the probes have attached You can visualize the locations where the probes have stuck to the nylon membrane
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Step 8: Develop film by dragging it to the developer
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What happens? The film is developed and shows the locations on the nylon membrane where the probes attached themselves to DNA fragments.
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The results Carmela Honey Candy
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