Fig. 3. Analysis of DNA fibers prepared from primary spermatocyte nuclei of D. melanogaster. (A-C) Staining with the DNA dye Hoechst 33258. (A'-C') Immunostaining produced by either Jel318 (yellow) or Jel466 (red) merged with the DNA staining (blue). (A') Jel318 specifically recognizes a long, continuous filament barely visible after Hoechst 33258 staining; (B') an almost integer loop occasionally visible in these preparations; image B is slightly overexposed compared with B', to show the DNA nature of the structure decorated by the antibody. (C') Jel466 recognizes a granular, dot-like matrix inside the kl-5 loop (see also Fig. 2); sometimes it is possible to see aligned dots along a DNA axis. Note that none of the antibodies shows cross reactions with the chromatin clumps which are present in these cells.