MOLECULAR CHARACTERIZATION AND CYTOLOGICAL MAPPING OF A NONREPETITIVEDNA-SEQUENCE REGION FROM THE W CHROMOSOME OF CHICKEN AND ITS USE AS AUNIVERSAL PROBE FOR SEXING CARINATAE BIRDS

A non-repetitive genomic DNA region of about 25 kb was cloned from the W chromosome of chicken using a genomic library prepared from a singl e W chromosome of the chicken. This region was mapped by fluorescence in situ hybridization (FISH) with mitotic and lampbrush chromosomes to a position between the major EcoRI family and the pericentromeric Xho I family on the W chromosome. A 0.6-kb EcoRI fragment (EE0.6) subclone d from this region consists of a sequence that can be obtained by the exon-trapping procedure and flanking sequences. Sequences, which are c losely similar to that of EE0.6, are widely conserved on the W chromos omes of Carinatae birds, as revealed by Southern blot hybridization to HindIII-digested female and male genomic DNAs from 18 species of bird s belonging to eight different taxonomic orders. The female sex of tho se birds can be determined by the presence of an unambiguous female-sp ecific band. For many species of birds, the female sex can also be det ermined by polymerase chain reaction (PCR) using a set of primers from the flanking sequences in the chicken EE0.6.