Animals develop according to a programed pattern – they follow one line from head to tail, and another from back to belly. In fruit fly embryos this pattern of development is orchestrated by a protein called dorsal, which switches certain genes on and off. Dorsal levels are spread unevenly around the embryo’s girth. The amount determines which genes are expressed where, which in turn dictates the fate of new cells. This embryo cross section shows the system at work. Each colour represents a different gene. At the top, where there is least dorsal protein, a gene called dpp (stained yellow) is turned on. At the bottom, high concentrations of dorsal switch on another gene (red). So this fluorescent pinwheel helps scientists understand how the right sorts of cells end up in the right place.
Written by Daniel Cossins
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences (the new name for the MRC Clinical Sciences Centre) the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.