An illustration of the role of the bicoid gene in the development of polarity in a Drosophila embryo. bicoid mRNA locates to the anterior pole of the developing oocyte. The protein Staufen is required for the microtubule-dependent localisation of bicoid mRNA. Here, fluorescent bicoid mRNA (green) injected into a Drosophila embryo recuits GFP-Staufen (Green) into large particles, which will then localise on the mitotic spindles. The yellow is an area of colocalisation of bicoid mRNA and GFP-Staufen.