Telomere clustering in spermatocytes deficient in SMC1β and SYCP3. (A) Percentage of nuclei showing internal or peripheral position of telo-FISH signals of either chromosome No. 1 (long), 12 (medium), or 19 (short). Spermatocytes from WT, Smc1β^−/−, and Smc1β^−/− Sycp3^−/− strains were analyzed (n = 60). Examples for internal or peripheral positions are shown in the images. Red, chromosome-specific cosmid telo-FISH; green, SYCP3. The arrows point to peripheral and internal telomere signals, respectively. (B) The percentage of spermatocytes that display clustered telomeres (bouquet stage) among spermatocytes I for the mouse strains indicated (n = 4,083 [WT], 4,111 [Smc1β^−/−], 4,056 [Sycp3^−/−], and 4,019 [Smc1β^−/−Sycp3^−/−]). The inset shows an example of a bouquet staining. Green, telo-FISH; red, satellite pericentromeric major satellite probe. Bars, 10 µm.