BAC clones mapped two by two on chicken metaphases. Three BAC clones were used: WAG137G04 (NOR), WAG523B09 (Y complex), WAG65G09 (B complex). NOR (red) and B complex (green) are located on the same chromosome (a), as for Y complex (green) and NOR (red) (b) and for Y complex (green) and B complex (red) (c). BAC clones WAG523B09 (green, Y complex) and WAG65G09 (red, B complex) are in the same nuclear area (d). WAG523B09 hybridizes several times the chromatin suggesting the presence of repeat sequences.