Chromosomal mapping of the U1 and U2 snRNA genes in meiotic cells from males. The probe type, sex chromosome system and name of species are shown for each cell. Chromosomes with positive hybridization signals and sex chromosomes are indicated in the images. Note the presence of U1 snDNA clusters in the interstitial region of the neo-XY chromosomes of E. minor, and the U2 snDNA clusters in the proximal region of the neo-Y chromosome of D. lilloanus. Bar = 5 μm.