FIG. 1.

The human β-globin locus on chromosome 11 with regulatory elements. The positions of globin genes as well as the relevant enhancer and silencer (Gazouli et al., 2009) elements are illustrated. The HPFH-1 and HPFH-6 enhancers are located within the two olfactory receptor genes, OR-1B (Feingold et al., 1999) and OR-H6 (Kosteas et al., 1997), respectively. In the deletional HPFH phenotype, one of the hypotheses proposes that distal enhancer elements (such as HPFH-2) juxtapose next to the γ-globin genes, leading to their activation during adult life. Color images available online at www.liebertonline.com/hum