Schematic representation of the chicken β-globin cluster and surrounding loci.

Boxes represent the folate receptor (FR), β-globin (ρ, βH, βA and ε) and chicken olfactory receptor (COR) genes (not to scale). Arrows indicate DNaseI hypersensitive sites. The core of the HS4 element is expanded to show the positions of the five in vitro footprinted sequences [11].