Fig. 3. HP-1 antibody staining pattern in mitotic nuclei from blastoderm male and female embryos. Left: DAPI staining. Right: merged image, with DAPI fluorescence in red and HP-1 immunolabeling in green. The 10 euchromatic chromosomes of the female complement are shown in A. Note the scattered chromosomal distribution of HP-1 immunostaining. (B,C) Chromosomes from male nuclei in early (B), and late (C) metaphase. HP-1 immunostaining is concentrated over heterochromatic chromosomes (arrowheads), with the euchromatic homologs lacking any labeling (small arrow in B indicates the secondary constriction corresponding to the nucleolus organizing region of a chromosome). Note that, in C, the five euchromatic chromosomes reached a high degree of condensation and the differentiation between euchromatic and heterochromatic chromosomes by DAPI staining is less apparent. Scale bar: 10 µm.