In Situ Gene Mapping of Two Genes Supports Independent Evolution of Sex Chromosomes in Cold-Adapted Antarctic Fish

Figure 3

Schematic representation of the tandem fusion (a) and centric fusion (b) originating the Y-chromosome from a supposed ancestral condition in C. hamatus and P. macropterus, respectively. The black bars on the ideogrammatic Y chromosomes indicate the sites of tandem or centric fusion on the secondary-Y chromosomes. The sex chromosomes from female (conserving the supposed ancestral condition) and male C. hamatus (a′) and P. macropterus (b′) are shown after in situ hybridization with a 5S rDNA probe and AFGP genes probe, respectively.