Fig. 3. Cohesin SMCs are associated with centromeres and chromosome arms in all 16 cells of each germ-line cyst. (A) A partial region 2A cyst from a wild-type chromosome spread preparation is stained for C(3)G (orange), SMC1/3 (white), DNA (blue) and CID (pink). SMC1/3 is enriched at the centromeres of all nuclei (solid arrows). In nuclei that contain C(3)G staining, SMC1/3 signal is thread-like. In pro-nurse cell nuclei that do not build SC, diffuse SMC1/3 staining indicates that cohesin subunits are associated with chromatin throughout the nuclei (open arrows). Bar, 5 µm. (B) Wild-type chromosome spread preparation shows that when the SC disassembles in a pro-nurse cell (left nucleus with only short linear stretches of C(3)G staining remaining), the diffuse SMC1/3 signal is similar in pattern and intensity to a nearby nucleus that does not contain appreciable C(3)G signal. Compare SMC1/3 staining within the two circles. Bar, 2 µm.