Download Genetic Engineering

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?
1
2
3
4
-------------GAATTC-------------------------------GAATTC--------------------GAATTC---------GAATTC----GAATTC----GAATTC-----------------------------------GAATTC------------1 -------------GA ATTC----------------------------2 ---GA ATTC--------------------GA ATTC------3 ---GA ATTC----GA ATTC----GA ATTC------4 ---------------------------------GA ATTC---------
Electrophoresis animation
Click here
How will the fragments appear
in a gel?
1 -------------GA ATTC----------------------------2 ---GA ATTC--------------------GA ATTC------3 ---GA ATTC----GA ATTC----GA ATTC------4 ---------------------------------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