A university study could explain why females may suffer worse outcomes of virus infection such as Covid-19. Researchers from the University of Dundee’s School of Life Sciences found the control of genes on X chromosomes in females can cause much wider effects on cells than previously realised. The X chromosome – of which females have two and men have only one – contains more than 1,000 genes that are vital for cell development. However, a double dose of such gene products can be lethal, meaning one of the two chromosomes in female cells shuts down in a process known as X chromosome inactivation (XCI).