Answer: fertilization of the egg
Role in axial patterning. Bicoid mRNA is actively localized to the anterior of the fruit fly egg during oogenesis along microtubules by the motor protein dynein and retained there through association with cortical actin. Translation of bicoid is regulated by its 3′ UTR and begins after egg deposition. Diffusion and convection within the syncytium produce an exponential gradient of Bicoid …
The Bicoid protein is a morphogen as well. The Nanos protein is a translational repressor protein. Bicoid has a DNA-binding homeodomain that binds both DNA and the nanos mRNA . Bicoid binds a specific RNA sequence in the 3′ untranslated region called the Bicoid 3′-UTR regulatory element of caudal mRNA and blocks translation .
Bicoid and Nanos both encode morphogens that have the opposite effect on Hunchback mRNA translation – Bicoid activates translation whereas Nanos represses it. As such Hunchback mRNA is translated so that Hunchback protein is present in the concentration gradient which decreases along the anterior – posterior axis.
Bicoid ist ein Protein des Modellorganismus Taufliege (Drosophila melanogaster) und anderer Dipteren-Arten. Es handelt sich um einen Transkriptionsfaktor der eine wichtige Rolle bei der Zelldifferenzierung in der frühen Keimesentwicklung (Embryogenese) spielt. Bicoid bzw. dessen Gradient i…