DNA FingerprintingDNA FingerprintingComparing DNA samples Comparing DNA samples

using gel electrophoresisusing gel electrophoresis

How is DNA fingerprinting How is DNA fingerprinting technology useful?technology useful?

Food identificationFood identification Mystery meatMystery meat Endangered speciesEndangered species

ForensicsForensics Crime scenesCrime scenes Overturning erroneous convictionsOverturning erroneous convictions Human remainsHuman remains

Paternity/maternityPaternity/maternity Child supportChild support Immigration Immigration

Health and medicineHealth and medicine Genetic disordersGenetic disorders Bone marrow transplantsBone marrow transplants Identifying pathogensIdentifying pathogens

How can we examine How can we examine DNA to look for DNA to look for similarities and similarities and

differences?differences?

ElectrophoresisElectrophoresis ““carry with electricity”carry with electricity”

DNA samples

from crime scene and suspects

Bacteria provide Bacteria provide tools to cut DNAtools to cut DNA

““DNA scissors” produced by bacteriaDNA scissors” produced by bacteria Adaptation to protect bacteria against virusesAdaptation to protect bacteria against viruses

Restriction EnzymesRestriction Enzymes More than 3000 known restriction enzymes, More than 3000 known restriction enzymes,

or “endonucleases”or “endonucleases” Each cuts at a specific DNA sequence called Each cuts at a specific DNA sequence called

a a restriction siterestriction site.. Restriction sites are palindromesRestriction sites are palindromes

How do restriction enzymes How do restriction enzymes work?work?

What happens when we cut all What happens when we cut all DNA samples with the same DNA samples with the same

restriction enzyme?restriction enzyme?11 -------------GAATTC------------------------------------------GAATTC-----------------------------

22 ---GAATTC--------------------GAATTC----------GAATTC--------------------GAATTC-------

33 ---GAATTC----GAATTC----GAATTC----------GAATTC----GAATTC----GAATTC-------

44 -----------------------------GAATTC------------------------------------------GAATTC-------------

1 -------------GA ATTC----------------------------- 2 ---GA ATTC--------------------GA ATTC-------3 ---GA ATTC----GA ATTC----GA ATTC-------4 ---------------------------------GA ATTC---------

Electrophoresis animationElectrophoresis animation

Click here

How will the fragments appear in a How will the fragments appear in a gel?gel?

1 -------------GA ATTC----------------------------- 1 -------------GA ATTC----------------------------- 2 ---GA ATTC--------------------GA ATTC-------2 ---GA ATTC--------------------GA ATTC-------3 ---GA ATTC----GA ATTC----GA ATTC-------3 ---GA ATTC----GA ATTC----GA ATTC-------4 ---------------------------------GA ATTC---------4 ---------------------------------GA ATTC---------

Electrophoresis ProcedureElectrophoresis Procedure

Cut DNA samples with restriction enzymesCut DNA samples with restriction enzymes Add loading dye to samplesAdd loading dye to samples Load samples in gel and apply chargeLoad samples in gel and apply charge DNA separates by size (small=fast)DNA separates by size (small=fast) Stain DNA in the gelStain DNA in the gel Bands appear where same-sized Bands appear where same-sized

fragments are located, forming a patternfragments are located, forming a pattern Compare patterns to find matchesCompare patterns to find matches

Pipette techniquePipette 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 pipetteThe disposable graduated pipette