During its gestation, the house mouse starts out as a single fertilized cell and three weeks later is ready to enter the world as a free-living pup composed of more than 500 million cells.
Scientists are eager to understand how the genome of the house mouse, Mus musculus, orchestrates this routine yet astounding transformation. Although its pregnancies are much shorter, the mouse shares many evolutionary commonalities with humans. It not only offers a useful scientific model of mammalian prenatal development, but also might reveal some basics of what happens during human pregnancies.
It has been difficult, however, to determine the gene activities that drive the timing and appearance of the hundreds of cell types that form a complete newborn mouse, with all its parts in the right place. Due in part to this vast number of cells, the genetic movers of mouse early embryonic development previously have been sampled coarsely at fairly long intervals, such as day to day observations.
