Normal mice develop from oocytes injected with spermatozoa with grossly misshapen heads.

Because in the mouse some structurally abnormal spermatozoa can penetrate oocytes, we decided to determine whether mouse oocytes fertilized by spermatozoa with grossly misshapen heads are able to develop normally. We injected such spermatozoa from BALB/c mice individually into mature oocytes of hybrid mice B6D2F1. Eighty to ninety percent of the oocytes were activated and developed into blastocysts in vitro and, when transferred to foster mothers, some developed into apparently normal fertile adults. This finding indicates that a proportion of abnormal spermatozoa carry all the genome and organelles necessary for normal embryonic development and growth to fertile maturity.