Figure 3.

Cohesin Binds to Distinct Regions on Polytene Chromosomes

(A) Polytene chromosomes of wild-type flies (w¹¹¹⁸) were stained with Rad21 antibodies (green) and DAPI (DNA, red). The lower panel shows a higher-magnification view (2.5×). The strongly DAPI-stained heterochromatic chromocenter (arrow) is devoid of Rad21 staining. The scale bars are 20 μm.

(B) Polytene chromosomes from flies expressing myc-tagged Rad21^TEV in addition to endogenous Rad21 were coimmunostained with antibodies against Rad21 (green) and myc (red). DNA was visualized with DAPI (blue). In the right two frames, part of one chromosome arm is shown at higher magnification with split Rad21- and myc channels. The scale bars are 20 μm in the left four frames and 10 μm in the right two frames.