DNA Fingerprinting

• We share 99.9% of our DNA with each other.

• That means the 0.1% of our DNA makes us unique.

• But that is still is over 3,000,000 differences!

• So what if we cut that DNA up with the same restriction enzymes, do you think we would have the same size fragments???

Two Major Steps Of DNA Fingerprinting

1. cut DNA w restriction enzymes•  Restriction •  Fragment•  Length•  Polymorphism

2. Gel Electrophoresis:Separate fragments from RFLP by...•  *Size (length)•  *Electric Charge 

http://www.lpscience.fatcow.com/jwanamaker/animations/Chrom&Elpho.html

Steps for Gel Electrophoresis

1. Obtain DNA sample2. Cut DNA with restriction enzymes3. Make a gel, put into gel box, fill box with buffer•  Buffer maintains pH and provides

ions for current to flow

4. Load DNA into "wells" of gel5. Turn on electrical charge•  DNA is negative - moves to positive6. Turn off power and see how fragments have traveled•  Shorter pieces travel farther•  Bands can be viewed with UV light

Figure 13.24Mixture ofDNA mol-ecules ofdifferentsizes

Cathode

Restriction fragments

Anode

Wells

Gel

Powersource

(a) Negatively charged DNA molecules will movetoward the positive electrode.

(b) Shorter molecules are impeded less thanlonger ones, so they move faster through the gel.

RFLP

• Is useful for comparing two alleles for a gene

It Takes a Lickin'...

• http://www.pbslearningmedia.org/asset/tdc02_int_creatednafp2/