Changes in a relatively small number of regulatory sequences help produce the large phenotypic differences between humans and chimpanzees. Illustrated here is a network of interacting genes for transcription factors that are differentially expressed in the brains of humans and chimpanzees and control the expression of other genes. Red circles represent transcription factors that are more highly expressed in the human brain; green circles represent transcription factors that are more highly expressed in the chimpanzee brain.
[Edwin Hadley, University of Illinois.]