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Gel Combs

January 14, 2010

After running a PCR, the next step is to run a Gel electrophoresis to separate and analyze the DNA sequences.
Gel combs are located in a gel rig to create wells for placement of the amplified DNA, and an agarose gel is poured into it:

The gel is allowed to cure briefly, and then the amplified DNA is introduced with a pipette:

A current is then introduced:

The proteins in the DNA move toward the cathode or anode depending on their charge, and at different rates depending on their molecular weight. They thus separate and can be analyzed spectroscopically:

Here is the simple camera rig and light box they use to photograph the gels:

And a digital image of the gel:

Close-up:

A Problem

The Anthropology Department runs thousands of these gels, and each well needs to be filled with the amplified DNA individually with a pipette. To speed the process, they purchased an 8-tip pipette, but they currently only own gel combs with 10 or more tines:

Solution

8-tine combs are available, but at nearly $60 apiece are a hardship for a small lab. We ventured that we could have them made at the Advanced Media Studio at a fraction of the price. AMS was very cooperative, and the process was quite simple:
1. We drew up an 8-tine comb with Vectorworks (any dimensionally accurate drawing program will do), exported it as an illustrator file, and brought it to AMS:
2. They cut four samples on the laser cutter:

Improvements:

Christina had the final combs cut out of black plastic instead of clear so that they would show up more easily on the lab benches. She also added a tab to give it greater thickness at the upper end, making it easier to hold.

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