Figure S11 Internal controls provided by the MAT locus. (A) Scheme of the MAT, HML and HMR loci. Nucleosomes are acetylated at the MAT locus but not at the two silenced HML and HMR loci [49]. Strains of type alpha, such as BY, have a single copy of the a1 sequence located at HMR and two copies of the alpha1 sequence: one at HML and the other at MAT. Strains of type a (such as RM) differ only at the MAT locus containing a1 instead of alpha1. Thus, H3K14 acetylated chromatin fractions are expected to be enriched in alpha1 DNA for BY and a1 DNA for RM. (B) Dosage of alpha1 and a1 sequences in ChIP fractions by real-time quantitative PCR (absolute quantification) as explained in methods. (C) Abundance of alpha1 and a1 sequences in the two strains was compared from raw intensity values of 23 and 22 microarray probes, respectively, interrogating the same fragments as those amplified in (B). 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