1. DNA Fingerprinting Techniques

2. RFLP Stands for Restriction Fragment Length Polymorphism
Takes advantage of differences in DNA between individuals that result in different size fragments when digested with restriction enzymes*
Cut specific DNA sequences
How many fragments will result when each of these alleles are digested with DdeI?
3 fragments
2 fragments

3. RFLP
To see RFLP, DNA is digested with the appropriate restriction enzymes and run on an agarose gel in a process called electrophoresis.

4. Gel Electrophoresis
Agarose gels are porous and will allow the DNA fragments to move through them
Electric current (running between a negative to positive pole) applied to the gel will cause the DNA (slightly negative charge) to be pulled through the gel towards the positive pole
DNA fragments will be separated by size

5. Which fragments will move the fastest? Small or Large?
Smaller fragments will move faster and farther down the gel than larger fragments
Once separated by electrophoresis, DNA fragments can be visualized using various techniques

6. Ethidium Bromide Staining
EtBr is a chemical that binds to DNA and glows in UV light.
We can “stain” our DNA bands by soaking the gel in EtBr.
When we expose the gel to UV light we will see a distinct banding pattern – a DNA fingerprint.

8. RFLP Animations
Animation #1
Animation #2

9. Time to Practice
“DNA Goes to the Races”

10. Interpreting a Paternity Test DNA fingerprint
Each individual inherits 50% of each parent’s DNA.
Half of your RFLP’s came from mom and half from dad
We can compare the DNA fingerprints of parents and children to determine paternity

11. What can we learn from the cases below?
Mom
Baby
Dad
Mom
Baby
Dad
Are mom and dad homozygous or heterozygous?
Is baby homozygous or heterozygous?
Could mom and dad be the parents?
Could mom and dad be the parents?
YES
YES

12. Activity Time
Let’s “Find a Family” using DNA fingerprints