Cover image

Cover In the middle, primary (blue) and secondary (green) I-element piRNA density in Drosophila ovaries is shown along the I-element sequence (black line). The piRNA populations for two isogenic Drosophila strains with different ancestor ages are shown above (young) and below (old) the line. The larger green area below the line illustrates the major increase of secondary piRNAs after aging of the ancestors, which confers to the progeny a high capacity to repress I-element transposition. Two smaller profiles (top) show duplicates on a smaller scale, and at the bottom is a reflection of the main profile. The figure is generated with R (R Development Core Team. 2010. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN 3-900051-07-0, http://www.R-project.org) using sequencing data obtained with NovoAlign (http://www.novocraft.com). (Cover illustration by Claudia Armenise. [For details, see Grentzinger et al., pp. 1877–1888.])