Supplemental Material for Warsinger-Pepe, Li, and Yamashita, 2020 Warsinger-PepeNatalie LiDuojia M. YamashitaYukiko 2020 Figure S1 shows representative images of diploid larval tissues revealing that heterochromatin formation aids in Y rDNA dominance in males. Figures S2 shows quantification of nucleolar dominance in polyploid tissues in wild type and mutant males. Figure S3 shows RNA <i>in situ </i>controls revealing that distinct ITS probes can differentially identify X rDNA variants. Figure S4 shows hybrid dysgenesis data for female nucleolar dominance crosses and that female nucleolar dominance is not influenced by parental origin. Figure S5 shows DNA FISH and IF images of the cytological characterization of the Xbb<sup>-</sup>YS chromosome. Reagents Table lists all relevant reagents used in this manuscript. Table S1 compiles the raw data of nucleolar dominance scoring for each relevant figure, organized by tab.