Gel Electrophoresis
http://biotrek.rdrake.org/img/gallery/33electrophoresis1_training.jpg
Definition
 Gel electrophoresis
is a technique used
to separate DNA
bands based on size
http://www.antibiotic.ru/en/mbio/pub/images/p233r2.gif
Quick Quiz
Gel electrophoresis separates molecular
products based on:
A.
B.
C.
D.
Shape
Size
Charge
Evolutionary similarity
Examples
 Gel Electrophoresis
is used to
visualize…
 Genomic DNA
 RNA
 PCR products
 Plasmids
 Restriction enzyme
digest products
http://www.steve.gb.com/images/science/agarose.jpg
Non-example
 Gel Electrophoresis is not used to…
 Separate DNA from the cell or from tissues
Agarose
 Neutral
polysaccharide
http://www.steve.gb.com/images/
 Harvested from
Rhodophyceae algal
cell walls
Agarose
 Alternating sugar units
form linear chains
 Cross-linking chains via
hydrogen bonds forms
porous matrix
 Heat breaks matrix
apart
 Cooling forms a matrix
with an “average” pore
size
http://www.bioscience-beads.com/images
Quick Quiz
When traveling through an agarose gel, larger
molecular products will migrate _________
smaller molecular products.
A. Faster than
B. Slower than
C. At the same rate
Why Run a Gel?
 Molecular weight
markers are DNA
fragments of known
size
 Comparison of sample
bands to markers
allows…
 Visible confirmation of
desired product
 Quantification of sample
DNA
http://www.biomedcentral.com/content/figures/1471-2180-5-63-2.jpg
How Gel Electrophoresis Works
http://www.sumanasinc.com/webcontent/anisamples/majorsbiology/
gelelectrophoresis.html
http://learn.genetics.utah.edu/units/biotech/gel
Quick Quiz
As DNA has a net _______ charge, it migrates
towards the gel box’s _________.
A.
B.
C.
D.
Positive; cathode
Positive; anode
Negative; cathode
Negative; anode
Visualizing DNA
 Ethidium Bromide
binds to DNA
 Fluorescence under
UV light makes
bands visible
http://www.lanl.gov/news/albums/bioscience/AnthraxUVplate.sized.jpg
Quick Quiz
The size of the molecular products is
determined by:
A.
B.
C.
D.
The intensity of the band
The percentage of agarose gel
Comparison with a molecular weight “ladder”
Being familiar with your gel and “eyeballing” it
Gel Electrophoresis
Prepare agarose gel
Melt, cool and add Ethidium Bromide. Mix thoroughly.
Pour into casting tray with comb and allow to solidify
Add running buffer, load samples and marker
Run gel at constant voltage until band separation occurs
View DNA on UV light box and document results
Quick Quiz
Buffer is used instead of water when making
and running gels because:
A. Buffer enhances the transmission of electric
currents in water
B. Buffer is more homogeneous than water
C. Buffer neutralizes the charge on molecular products
prior to electrophoresis
D. Buffers can be customized based upon the
electrophoresis protocol
Troubleshooting Guide
DNA Science: A First Course in Recombinant DNA Technology, by David A. Micklos and Greg A. Freyer
END
Resources
 Gel Electrophoresis Handout
 DNA Science: A First Course in Recombinant DNA
Technology, by David A. Micklos and Greg A. Freyer
 http://www.sumanasinc.com/webcontent/anisamples/
majorsbiology/gelelectrophoresis.html
 http://learn.genetics.utah.edu/units/biotech/gel
California State Chemistry Standards
Grades 9-12
2. Properties of matter result from the ability of atoms to form
bonds…
6. Solutions are homogenous mixtures of two or more
substances
10b. Students know the bonding characteristics of carbon…
California State Biology Standards
Grades 9-12
5d. Students know the general structure and function of DNA
California State
Investigation and Experimentation
Standards
Grade 7
a. Select and use appropriate tools and technology to perform
tests, collect data, analyze relationships, and display data
Grades 9-12
c. Identify possible reasons for inconsistent results, such as
sources of error or uncontrolled conditions
d. Formulate explanations by using logic and evidence
k. Recognize the cumulative nature of scientific evidence
l. Analyze situations and solve problems that require combining
and applying concepts from more than one area of science
National Standards
Grades 6-12
Content Standard A: Science as Inquiry
Content Standard C: Life Science
Content Standard E: Science and Technology