Karyotypes of Ura+His+ candidate disomes. Haploid strains carrying a modified chromosome were treated with galactose and plated to select Ura+His+ papillae as described in the text. To assess chromosome copy number, DNA from Ura+His+ isolates (red) was combined with DNA from a haploid parent strain (green) and hybridized to microarrays containing the genomic collection of yeast open reading frames. Log-transformed red:green ratios are displayed in histogram format for each gene along each chromosome, using the Karyoscope viewer of Java Treeview . Results from representative arrays are shown (disomic III: KAY495; disomic IV: KAY638; disomic VI: KAY605; disomic VI, XII: KAY679; disomic II, VI, XII: KAY681). Complete data from all arrays are deposited at GEO .