Distribution of XhoI and EcoRI family repetitive DNA sequences into separate domains in the chicken W chromosome.

Fluorescence in situ hybridization using as probes three biotinylated or digoxigenin-labeled chicken W chromosome-specific repeating DNA units (0.7 and 1.1 kb XhoI family and 1.2 kb EcoRI family units) suggested that a large fraction of one arm of the W chromosome was occupied by the EcoRI family sequences and that pericentromeric regions were widely occupied by the XhoI family sequences. A minor fraction of the EcoRI family was also present in a narrow region in the proximal half of the other arm. There was a region in the distal half of the latter arm where sequences from neither family hybridized. Evolutionary aspects of the presence of different domains occupied by different repetitive families and the significance of the unhybridized distal region are discussed.