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

Today’s laboratory: DNA fingerprinting in a hypothetical forensics team investigation

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 A Criminal Case

Step One: Cut up your DNA! Crime Suspect Suspect Scene One Two

Step Two: Load Up Your Gel Crime Scene Suspect One Suspect Two Look at those RFLP’s!

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.