Histone modification state of a unique sequence with a different positioning within 2 alleles of the β-globin locus. (A) Schematic of the region of the β-globin locus between the β1- and β2-globin genes for the D and S alleles. The block of unique sequence that occupies different relative positions within each allele is indicated by the thicker bar with a light fill, whereas the large insertions of repetitive DNA specific for each allele are indicated by thicker bars with dark fill. Positions of PCR amplimers used in analysis of ChIP assays are shown by the short bars beneath the representation of each allele. * represents the amplimer located within the unique sequence; “X,” an amplimer within a unique region that is found in the D but not the S allele. (B) Bar graphs showing enrichment levels for H3Ac (top) and H3K4 dimethyl (bottom), relative to inactive gene loci. Bars within the dark-shaded regions represent portions of the locus that are common to both the D and S alleles; lightly shaded regions, portions of the locus unique to the D or S alleles. * represents enrichments observed for the translocated unique sequence common to D and S; “X,” enrichment observed for the sequence unique to D.