Diagram of the human β-globin gene domain showing the arrangement of the five β-globin genes, the position of the six identified DNase I hypersensitive (HS) sites (arrows), and the location of the 5′HS2 and 3′β enhancer elements (E). The expanded view of the G γ gene promoter region shows the recognition sites for the DNA-binding proteins GATA-1 and OBP.