Fibre-fluorescence in situ hybridization unravels apparently seven DAZ genes or pseudogenes clustered within a Y-chromosome region frequently deleted in azoospermic males.

Using the technique of 'fibre-FISH' (fluorescence in situ hybridization), we describe the direct visualization of seven longer DAZ signal stretches and in addition a maximum of four isolated single DAZ signals on Y-chromatin fibres of four different individuals. These seven longer DAZ signal stretches may represent seven DAZ genes or pseudogenes, whereas the single DAZ signals may represent truncated DAZ genes.