<i>Mus81^−/−</i> male mice have reduced testes size and sperm number.

<p>Testes from WT (A) and <i>Mus81^−/−</i> (B) mice were removed, weighed and photographed. Scale bar 5 mm. C, D) Respectively, WT and <i>Mus81^−/−</i> testes sections stained with H&E. E, F) WT and <i>Mus81^−/−</i> testes sections stained with antibody to GCNA-1 raised in rat (red). G, H) WT and <i>Mus81^−/−</i> testes sections TUNEL stained for apoptotic cells (dark brown) and counter stained with methyl green. I) Average number of apoptotic cells per tubule in WT and <i>Mus81^−/−</i> testis sections, which are significantly different between the two genotypes (P = 0.0073).