Download Gel Electrophoresis DNA Fingerprinting

Gel Electrophoresis
DNA Fingerprinting
DNA Analysis
• How are DNA molecules analyzed.
• Restriction enzyme digestion of DNA
molecules.
• Gel electrophoresis to separate DNA
fragments of different sizes.
Restriction Enzymes
Where did they come from?
• Bacteria!
• Natural defense against
viral infections
• Cut up DNA at various
bases sequences
• May leave a “stickey
end”
• May leave “blunt end”
Restriction Digestion of DNA
Blunt End
Sticky End
Restriction Map Comparison
DNA Analysis
• How are DNA molecules analyzed.
• Restriction Nuclease digestion of DNA
molecules.
• Gel electrophoresis to separate DNA
fragments of different sizes.
DNA Gel Electrophoresis
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Today’s laboratory:
DNA fingerprinting in a
hypothetical forensics team
investigation
A
Criminal
Case
• In this hypothetical case, DNA was extracted
from samples obtained from the five possible
suspects, and the crime scene sample
• You will cleave the DNA with a restriction
enzyme and simulated a “mock” DNA
fingerprint analysis using Southern Blotting
Step One: Cut up your DNA!
Crime
Scene
Suspect Suspect
One
Two
Step Two: Load Up Your Gel
Look at
those
RFLP’s!
Crime Scene
Suspect One
Suspect Two
Step Three: It’s Blotting Time
Step Four: Hybridize using DNA
probe
Step Five: Take a picture!
Typical Southern Blot
Gel Electrophoresis vs.
Southern Blots
Electrophoresis
• Shows you ALL
DNA fragments that
result from restriction
enzyme digest
• All possible RFLP’s
are shown
Southern Blots
• Additional step after
electrophoresis
• Looks from specific
short DNA sequence
inside of RFLP’s
• Uses radioactive
material
• Much more specific
than gels.