JUMPING GENES AND SEX GENES. “Here, recent evidence assigns transposable elements a role in having moved the male sex-determining gene to other chromosomes. As result, the Y chromosome is a different linkage group in several salmonid species. If large pieces or the entire Y are translocated to an autosome, so-called “neo-Y chromosomes” and multiple sex-chromosome systems are created.”
http://www.pnas.org/content/112/34/10575.full