| Type | MGI:General | Description | mutant sperm fail to fertilize oocytes in vivo and in vitro during IVF assays, many mutant sperm remain associated with either the zona pellucida of intact oocytes or the cell membrane of zonaâÂÂfree oocytes/zygotes mutant sperm bind to the zona pellucida surrounding 2âÂÂcell embryos formed by IVF with wildâÂÂtype sperm, indicating failure to react to normal zona modifications that prevent polyspermy |