Extended Data Fig. 3: Genome structure of the living ancestor.

Each coloured bar represents a chromosome, with dark tones representing S. paradoxus DNA and light tones representing S. cerevisiae DNA. Dark blocks within S. cerevisiae chromosomes represent S. paradoxus LOH, and light blocks within S. paradoxus chromosomes represent S. cerevisiae LOH. White circles indicate centromeres and numbers (from 1 to 5) annotate the recombination breakpoints of the gross chromosomal rearrangements listed in the top-right box. Subgenome assignment for rearranged chromosomes is based on centromere flanking sequences. Genomic coordinates of S. cerevisiae and S. paradoxus chromosomes are based on the genome assemblies of DBVPG6765 and CBS432 strains, respectively. We cannot confidently say whether intrinsic (genetic) or extrinsic (environmentally induced) genome instability explain the astounding genome instability signature, nor we can say whether it emerged from a single event or accumulated gradually.