Fig. 4. Spo11^+/– early pachytene cells exhibit the same number of S-foci but contain more L-foci than Spo11^+/+ early pachytene cells. (A,B) Quantification of -H2AX containing S-foci (A) and L-foci (B) in early and late Spo11^+/+ and Spo11^+/– pachytene cells (black and white bars, respectively). Bars represent mean numbers ±s.e.m. for each experimental group (n=3). Statistical comparisons between Spo11^+/+ and Spo11^+/– mice at early and late pachytene were performed using the Mann-Whitney U test. Significance is ^***P<0.001. (C) Distinct repartition of L-foci in Spo11^+/– and Spo11^+/+ pachytene spermatocytes. Pachytene nuclei of Spo11^+/+ mice (black and dark gray bars) and Spo11^+/– mice (light gray and white bars) were classified according to their number of L-foci.