teaching electrophoresis to freshmen (fwd)

David L. Robinson dlrobi02 at HOMER.LOUISVILLE.EDU
Sun Jul 7 17:07:09 EST 1996


Keeping in line with the purpose of this group I thought I would quickly 
summarize the answers I got to a question I posed a couple of weeks ago 
about what might be the best way to demonstrate gel electrophoresis to 
freshmen. I received more than 20 replies so I will try to keep it 
short. Email me if you want more of the details.

Here are some of the suggestions:

1) In addition to xylene cyanol and BPB use Orange G, Ponceau Red, 
methylene green, Pyronine Y.

2) Methylene blue travels in the opposite direction of BPB, so place your 
wells halfway and they will move opposite to one another.

3) Use cake coloring

4) Use common food coloring...they separate fine in agarose gels.

5) Add india ink to whatever dyes you use to "cover up" the color while 
loading

6) Use the Molecular Weight Kits that are out now that feature 
different colored markers....lots of companies sell these.

7) Do column chromatography of something like hemoglobin.

8) If don't have traditional gel boxes pour the gels on glass slides 
(microscope slides).....

9) Other interesting comments about laboratory pedagogy...1) .are freshmen 
sophisticated enough to understand pKa and deprotonation?? ....2) use a 
"conceptual change" teaching model in the lab where you start off with 
what the students already know and then let them experiment and see if 
they can explain what they see based on these preconceptions. Then give 
them the real theory behind electrophoresis after they do the initial study.

Thanks again for all who answered this query!

Dave Robinson
Biology Department
Bellarmine College
Louisville, KY



) If place the gel on an overhead projector the entire class can see the 
gel (even as it runs).




---------- Forwarded message ----------
Date: 17 Jun 1996 16:22:38 -0700
From: David L. Robinson <dlrobi02 at homer.louisville.edu>
To: plant-ed at net.bio.net
Subject: teaching electrophoresis to freshmen


I am currently developing the laboratory component of a freshman, 
introductory biology class (for majors) that I teach in the fall. 
I want to demonstrate electrophoresis in lab, and am trying to 
figure out the most effective way to do it. Does anyone have any 
good ideas?

I know I could do a demonstration SDS-protein gel showing the protein 
profiles of different species/tissues, or I could do lambda 
restriction digests and run a DNA gel, but: 1) I only have 3 hours per
lab period for each group of students, 2) I teach multiple sections so this 
would be really a strain in terms of time and expense, 3) I'd rather not 
have a bunch of 18-year-olds playing around with things like acrylamide, 
ethidium bromide, etc. 4) I could just as easily show publication-quality 
photos of protein or DNA gels that are already in the literature 
or textbooks....what I really want them to appreciate is the *concept* 
of electrophoresis.....that you can separate molecules based on their 
size, charge and shape using an electric field. Once they understand 
that then they can start to deal with actual protein/DNA/RNA gels.

Last year, after I had them do paper chromatography exercises in 
separating chlorophyll and then amino acids I was able to just say that 
electrophoresis was "sort of like that except.....la la la". But I am 
not sure paper chromatography is conceptually a real good analogy for 
electrophoresis! Plus, I would like them to at least *see* some of the basic 
equipment that is used in cellular/molecular biology even if they don't get 
to actually use it themselves.

Now my idea is to pour an agarose gel for them, and load a well with 
a single, dark solution that would be a mixture of different dyes and then 
apply current. The dyes would move at different rates and 
separate out. In my imagination they would see lots of bands of red, blue, 
green, etc that had been separated by electric force. That would be the 
end of it...without any other steps I would have demonstrated the basic 
process of electrophoresis. Comments?????

Does anyone have any good ideas for what dyes would be good for this?
I can use bromophenol blue and xylene cyanole as they are different in 
color and mobility in an agarose system.....what other dyes of different 
color and mobility can I add to this mixture?

Thanks for any advice.

Dave Lowell Robinson      dlrobi02 at homer.louisville.edu
Biology Department
Bellarmine College
Louisville, KY 






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