Opening (image) University of Helsinki Caption Given its unique nature, the X chromosome has often been neglected when performing large-scale genetic studies. Because women have two copies of this chromosome and men only one, identifying genetic associations with X chromosomal genes can be particularly valuable in helping us to understand why some characteristics differ between sexes. Credit Taru Tukiainen Usage Restrictions None 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.