Spots and Stripes

I’m too busy grading Virology now to be posting, but some stories are too good to miss. Amid stem cell cures and global climate warnings, some scientists spend their come on matters of true importance: How the cheetah got its spots (or stripes, as may be). They’ve found two genes responsible: Taqpep and Edn3.

How they think it works–in tabby house cats, as well as cheetahs:

(1) The skin makes agouti protein, which turns off melanocortin, which stops hair follicles from making black and makes yellow instead.

(2) The Taqpep gene establishes a “prepattern”  which will allow follicles to make black pigment in alternating spots.

(3) The Edn3 protein turns on production of black in those spots.

(4) But if Taqpep is mutant–the prepattern is disrupted, and you get black stripes instead.

Yes, I think this one’s destined for the biology textbooks.