DNA Fingerprinting
DNA Fingerprint
Step One
• Collect the sample! • What do you think are the most common sources of DNA samples for forensic scientists?
Step Two
• Extract and purify the DNA. • Much the same as what we did with the Strawberry!!
Step Three
• Cut the DNA! • What do we use the cut DNA molecules?
Step Four
• Sort the DNA by length! • Big pieces = slow • Small pieces = fast
Sort by Length
• DNA has a negative charge. • Electrophoresis machine has a positively charged probe on one end.
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.
Step # 6
• Radioactive probes are attached to the DNA fragments.
Lets practice!!!
• DNA strand: AATCCGAATC
• DNA strand: TACCGATTCG
Step # 7
* Nylon
sheet with DNA fragments attached to radioactive markers is put into an x-ray machine.
End Result!!!
Step 8
• Analyze and compare results!
Do we have a match?
blood stain Bob Sue Juan Lakisha
Do we have a match?
blood stain Bob Sue Juan Lakisha