Gap gene expression patterns are activated by coordinate genes

(a) (b) Bicoid protein 0 ‘ ‘ hunchback Bicoid binding SItes gene Posterior - - ::-i If Bicoid protein binding directly l activates hunchback transcription. ‘ Regulatory interactions with l coordinate genes help define l hunchback expression domain. Anterior hunchback expression Maternally supplied mRNA in embryo Biwid adivates Nanos represses ():!:!:2£— hunchback translation of transcription hunchback mRNA Hunchback :::!__|:_ ( 'Successive deletions H of Bicoid binding sites Protein expression in early embryo result In progressive ‘ loss of hunchback mRNA expression.