Extended Data Fig. 8: Oxford grid between sea lamprey germline chromosomes and chordate linkage groups (CLGs).

Circles show the number of orthologous genes between germline chromosomes of sea lamprey (Petromyzon marinus, PMA, denoted scaff_XXXXX following Smith et al.) and the seventeen CLGs described in the main text. As in Extended Data Fig. 6 the area of each circle is proportional to the number of orthologous genes for each chromosome-CLG pair, and the color indicates the significance of the association relative to a null model in which the position of the orthologous genes are randomly shuffled. Sea lamprey chromosomes and CLGs are both sorted to exhibit the striking correspondence between them. Each of the 17 CLGs is represented by at least one lamprey chromosome, and typically 6-8 lamprey chromosomes are associated with teach CLG. Compare Fig. 4b of Smith and Keinath 2015, which compares lamprey chromosomes to ‘putative ancestral linkage groups’ derived by Putnam 2008 through clustering of amphioxus scaffolds These putative ancestral linkage groups are in 1:1 correspondence with the CLGs shown here to be represented as large chromosomal segments of amphioxus.