Fig. 4. Mid-cleavage male embryos treated for 4 hours with pchet2 dsRNA exhibit a dramatic loss in facultative heterochromatinisation of the paternal chromosome set. (A) DAPI staining of a 128-256-nuclei male embryo treated for 4 hours with pchet2 dsRNA showing a loss of strongly staining DAPI-positive chromocenters. These male embryos can only be distinguished from female embryos because of male-specific chromocenter remnants (arrow in A'). (A") C1A9 staining is not detectable in these embryos. (B-B") In control mock-treated embryos typical, bright, DAPI-positive chromocenters can be seen (B and B') that are also positive for C1A9 staining (merged image in B"); DAPI staining (red), C1A9 staining (green). Bars, 10 µm.