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Tuesday, February 10, 2004

A spoonful of sugar...

My main project in the lab involves regulating gene expression in mice using a technology called the Tet-off system, a genetic trick that is commonly used these days in developmental biology. The exact strategy is a bit complicated, but it boils down to the idea that the gene I'm interested in will be expressed UNLESS I feed the mice tetracycline. That is, when I give the mice the antibiotic, the gene should turn off. Hence, Tet-off. I could also have done it the other way around using the Tet-on system such that the gene would not be expressed UNTIL I fed the mice tetracycline. Note: either way, I must administer tetracycline.

There are three standard ways to get tetracycline into a mouse: add it to the food, add it to the water, or inject it. It is quite important for my experiment that the level of the drug be high enough to completely repress gene expression, and I must determine this empirically. This is made somewhat difficult by the fact that tetracycline and a related antibiotic, doxycycline, degrade very quickly. Therefore, if the mouse chooses not to eat some its tetracycline-laced food for a while, the level of antibiotic in its bloodstream might drop low enough to allow my gene to come back on. For the mouse, this is irrelevant. For my experiment, this is very bad.

Thus was my motivation to answer the question: If I were a mouse, would I eat this tetracycline-laced food?

In short, the answer is an unequivocal "no". Discovery number one is that mouse food, while not being good, is not actively bad. You could eat it if you had to, but you wouldn't enjoy it. It is possible that mice like it. It's dry and plain and grainy, with a hint of cardboard flavor. I felt that if I were a mouse, I would prefer it to, say, dry oatmeal, but I wouldn't rate it anywhere near cheese or peanut butter.

Once the tetracycline was added, however, it was horrible. It sort of reminded me of the time I made corn bread using baking soda instead of baking powder. Very bitter, somewhat metallic, definitely wrong. Luckily, the bitterness was largely counteracted by adding sugar. To get the tetracycline into the food, which starts out as dry pellets like dog chow, I had soaked it in water to make it soft. Then I added the antibiotic and the sugar, kneaded it, and rolled it into little cookies that look an awful lot like my great grandmother's rum balls.

Now the question is: If I bring these to lab meeting (minus the tetracycline), will my labmates eat them? Heads up, Charlie.

(Disclaimer: Kids, don't be eating stuff from the lab. Its a bad idea. )

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