A physical map of the human Y chromosome

The non-recombining region of the human Y chromosome (NRY), which comprises 95% of the chromosome, does not undergo sexual recombination and is presen t only in males. An understanding of its biological functions has begun to emerge from DNA studies of individuals with partial Y chromosomes, coupled with molecular characterization of genes implicated in gonadal sex reversal , Turner syndrome, graft rejection and spermatogenic failure(1,2). But mapp ing strategies applied successfully elsewhere in the genome have faltered i n the NRY, where there is no meiotic recombination map and intrachromosomal repetitive sequences are abundant(3). Here we report a high-resolution phy sical map of the euchromatic, centromeric and heterochromatic regions of th e NRY and its construction by unusual methods, including genomic clone subt raction(4) and dissection of sequence family variants(5). Of the map's 758 DNA markers, 136 have multiple locations in the NRY, reflecting its unusual ly repetitive sequence composition. The markers anchor 1,038 bacterial arti ficial chromosome clones, 199 of which form a tiling path for sequencing.