Bet on positional information.
Wolpert
L
L
D000818:Animals; D005075:Biological Evolution; D002080:Butterflies / Q000196:embryology / Q000235:genetics; D002454:Cell Differentiation / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004330:Drosophila; D029721:Drosophila Proteins; D005801:Genes, Homeobox; D018398:Homeodomain Proteins; D007313:Insecta / Q000196:embryology* / Q000235:genetics; D014157:Transcription Factors
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D014157:Transcription Factors; C066177:Ubx protein, Drosophila