Mutation Causes Sperm Production to Halt (IMAGE) University of Pennsylvania Caption A biopsy of the testis of an infertile man, who had a mutation in the TEX11 gene, shows the precursors of sperm, but no mature sperm. Credit University of Pennsylvania Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.