


The DNA of the chromosomes is divided up into genes. The genes determine the features a person inherits from his or her parents, such as blood type and other characteristics, including risks for developing certain diseases. Changes in chromosomes or genes may cause changes in certain body processes or functions. These changes may be undetectable or may cause genetic diseases, such as hemophilia or Down syndrome. Gene changes can be passed from parents to children or can occur through a new mutation.

