Figure 1.

The Drosophila F element has maintained its heterochromatic properties in four different Drosophila species. (Left) Immunofluorescent staining of polytene chromosomes using H3K9me2-specific antibodies shows that the D. melanogaster, D. erecta, D. mojavensis, and D. grimshawi F elements (colored arrows) are enriched in H3K9me2 (a mark of heterochromatin). (Right) Phylogenetic tree of the Drosophila genomes sequenced by the Drosophila 12 Genomes Consortium (Powell 1997). The colored stars next to the species names in the phylogenetic tree denote the species analyzed in this study; the same color scheme is used in this and subsequent figures.