It has been proposed that the pseudoautosomal region of mammals has evolved by sequential addition of autosomal material onto the X and Y chromosomes followed by movement of the pseudoautosomal boundary to create X-unique regions. We have previously described a gene, Fxy, that spans the pseudoautosomal boundary in mice such that the first three exons of the gene are located on the X chromosome, but the remainder of the gene is located on both X and Y chromosomes. Therefore, this gene might be in a state of transition between pseudoautosomal and X-unique locations. In support of this theory...

It has been proposed that the pseudoautosomal region of mammals has evolved by sequential addition of autosomal material onto the X and Y chromosomes followed by movement of the pseudoautosomal boundary to create X-unique regions. We have previously described a gene, Fxy, that spans the pseudoautosomal boundary in mice such that the first three exons of the gene are located on the X chromosome, but the remainder of the gene is located on both X and Y chromosomes. Therefore, this gene might be in a state of transition between pseudoautosomal and X-unique locations. In support of this theory we show here that the human FXY gene is located in Xp22.3 in humans, proximal to the pseudoautosomal boundary.