A team led by researchers at the Johns Hopkins School of Medicine has found that several inherited traits in the mouse genome break the rules Gregor Mendel laid down in the 19th century about how genes work. This is not because the genes mutate but because of chemical modifications of the genome that can jump across generations, change depending on whether an animal is male or female, and even copy themselves from one copy of a gene to another.

Their findings were reported recently in Nature Genetics.