The genomic structure of the clusters of α-like and β-like globin genes, on chromosomes 16 and 11, in human beings. The functional α-like genes are shown in dark blue and the pseudogenes are in light blue; 2 of these (μ and θ-1) code for small amounts of RNA. The functional β-like genes are shown in light green. The important control elements, HS-40 and the LCR, discussed in the text, are also shown at their approximate locations. The α-gene cluster is approximately two thirds of the length of the β-gene cluster; it is transcribed from telomere toward centromere, the opposite of the β cluster. The various hemoglobin species that are formed from these genes, with their prime developmental stages, are shown in the lower part of the figure. Illustration by Alice Y. Chen.