Figure 2

Maternal piRNAs suppress hybrid dysgenesis in P-M crosses. Crossing schemes on the left represent crosses of males of a strong P strain (Har) to females from different strains: w¹¹¹⁸ is an M strain lacking P-elements; Lk carries two P-element copies in the subtelomeric region; NA possesses a truncated P-element in the subtelomeric region of the X chromosome. The numbers in the rectangles beneath each cross are the P-element copy number per haploid genome. The P-specific piRNA density across the P-element in the ovaries of F1 daughters of each cross is depicted schematically on the right. piRNAs (wavy lines) that are antisense with respect to the P-element are in red; sense ones are in green. The truncated P-element in the NA strain is shown at the top in relation to a full-length P-element.