Fig. 1.

Spermatocytes from wild mammals have more crossover markers than cells from domestic mammals. Spermatocytes from dog (A), wolf (B), goat (D), ibex (E), sheep (G), and mouflon (H) immunostained against the crossover marker MLH1 (red) and the synaptonemal complex protein SYCP3 (green), which allows to visualize chromosome axes. DNA is counter-stained with DAPI (blue). Scatterplots display the total number of MLH1 foci found in each spermatocyte, and black lines represent the average number of foci found in each species (C, F, and I). Domestic species, green; wild species, red.