Chromatin immunoprecipitation quantitative PCR (ChIP-qPCR) characterisation of the α globin chromatin bivalency. (a) Sequential ChIP with H3K27me3 followed by H3K4me3 antibody. HOXA3 intron represents an H3K27me3 genomic region; HAND1 and GATA6 promoters are control bivalent promoters. (b) Sequential ChIP with H3K4me3 followed by H3K27me3 antibody. LUC7L and ACTB promoter are H3K4me3 modified promoters. The error bars show the standard deviation of three independent ChIP-qPCR experiments.