DNA Fingerprinting Comparing DNA samples using gel electrophoresis

How is DNA fingerprinting technology useful?  Food identification  Mystery meat  Endangered species  Forensics  Crime scenes  Overturning erroneous convictions  Human remains

 Paternity/maternity  Child support  Immigration  Health and medicine  Genetic disorders  Bone marrow transplants  Identifying pathogens

How can we examine DNA to look for similarities and differences?  Electrophoresis  “carry with electricity”

DNA samples from crime scene and suspects

Bacteria provide tools to cut DNA  “DNA scissors” produced by bacteria  Adaptation to protect bacteria against viruses

Restriction Enzymes  More than 3000 known restriction enzymes, or “endonucleases”  Each cuts at a specific DNA sequence called a restriction site.  Restriction sites are palindromes

How do restriction enzymes work?

What happens when we cut all DNA samples with the same restriction enzyme? GAATTC GAATTC GAATTC GAATTC----GAATTC----GAATTC GAATTC GA ATTC GA ATTC GA ATTC GA ATTC----GA ATTC----GA ATTC GA ATTC

Electrophoresis animation Click here

How will the fragments appear in a gel? GA ATTC GA ATTC GA ATTC GA ATTC----GA ATTC----GA ATTC GA ATTC

Electrophoresis Procedure  Cut DNA samples with restriction enzymes  Add loading dye to samples  Load samples in gel and apply charge  DNA separates by size (small=fast)  Stain DNA in the gel  Bands appear where same-sized fragments are located, forming a pattern  Compare patterns to find matches

Pipette technique Find well opening with tip Depress plunger s..l..o..w..l..y… Watch for air bubbles New tip for each sample!

The disposable graduated pipette