Abstract
There is an intricate network of molecules called cell fate determinants that instruct the cells of the embryo to take on either an anterior or posterior fate. In a lively Perspective, Lehmann and her colleagues discuss new findings in the fruit fly that identify a key protein, PAR-1, which ensures that the cell fate determinants are themselves located in the correct region of the oocyte. In this way, the anterior-posterior axis is set up in the fruit fly egg before fertilization.
