Total RNA was isolated from adult testes with the RNeasy Mini Kit (Qiagen, http://www.qiagen.com), and 4.0 μg was oligo dT–primed and reverse-transcribed with Superscript II (Stratagene, http://www.stratagene.com). The entire Trip13 protein-coding sequence was amplified with primers 5′-ATGGACGAGGCGGTG-3′ and 5′-TCAAACATAAGCTGAAAGTT-3′. The cycling conditions were: 94 °C 2 min; 94 °C 30s, 55 °C 45 s, and 72 °C 80 s for 35 cycles; and 72 °C 2 min. The primers for amplifying the Med31 coding sequence as control were : 5′-ATGGCCGCGGCCGTCGCTATGG-3′ and 5′-TCATTTCCCTGCTGTGTTATTCTGCTGCTGCTGC-3′. The cycling conditions were: 94 °C 2 min; 94 °C 30 s, 55 °C 30 s, and 72 °C 35 s for 35 cycles; and 72 °C 2 min.