Thus, while some Morn2–/– spermatozoa are competent for penetrating the ZP and fusing with oocytes, they could not complete fertilization in vivo, suggesting that the infertility of Morn2–/– mice may be due to the inability of sperm to swim to oocytes at the appropriate time, rather than the dysfunction in sperm-egg fusion. This evidence concerns the gene MORN2 and Infertility.