Same Gene - Different Function
Differences in development: often different regulation of genes
Humans & chimpanzees: 98.7% identical DNA but different patterns of gene transcription activity
Most developments controlled by family of genes; differences in transcription among genes of one family:e.g. Tbx5 for limb development; Pax6 for eye development
mouse Pax6 gene in fruit fly reduced Pax6 expression