X or Y? (IMAGE) Michigan Medicine - University of Michigan Caption Researchers find genes that skew sex ratio in mice. Credit Leila Mullison, University of Michigan Stamps School of Art and Design Usage Restrictions with permission from Leila Mullison. Contact PIO 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.