Yaël: What are we doing today, Don?

Don: Well, Yael, on this Moment of Science we're going to talk about lab mice.

Y: Oh, the little white ones?

D: Actually, the standard lab mouse these days is black, with a nice glossy coat. That's      the kind of mouse that went on the space shuttle and was used as a model for the      mouse genome-sequencing project.

Y: Why are they black?

D: Jackson Laboratory in Maine made the mouse the number-one research model and      they chose a black mouse as their standard, although the mice come in other colors      too. Scientists can order something like 3,300 varieties.

Y: Wow. Why so many?

D: Each different mouse strain serves as a model for a variety of human diseases and      disorders. For instance, you can get a "knock-out" mouse.

Y: A really sexy mouse?

D: No, it's a mouse with a deleted gene. You take out a gene to see what it does. They      also have "knock-in" mice that have a gene added in. And "transgenic" mice, where      they add in genes that mice don't normally have in order to recreate human-only      diseases.

Y: But wouldn't scientists need identical mice to standardize their research results?

D: Yes, exactly. That's why the mice are inbred for 20 generations--to create a colony      of genetic twins--and also to give them a very specific genetic profile, such as a      model for human diabetes. It doesn't take as long as you might think to produce the      mice because they can have a litter every 21 days.

Y: So, how do they get the mice to breed so often?

D: With a cheesy pick-up line, of course!  

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