Practice question

Anterior organizing center in Drosophila embryo is established by bicoid mRNA localization to anterior cortex mediated by Exuperantia, Swallow and Staufen RNA-binding proteins during oogenesis. Upon egg deposition, translation creates steep anterior-to-posterior Bicoid protein gradient acting as morphogen within syncytium. Bicoid homeodomain binds DNA to activate transcription of anterior gap genes like hunchback, orthodenticle and buttonhead, while also binding caudal mRNA to repress its translation anteriorly. High Bicoid concentration specifies acron and cephalic segments. Loss transforms anterior into posterior structures, demonstrating essential anterior patterning role.