(Lansing State Journal, March 2, 1994)
When a disease is due specifically to changes in a person's complement of DNA, it is called a genetic disease. There are a few dozen genetic diseases that are known to be present in the human population. Some of the more widely known genetic diseases include hemophilia, phenylketonuria, cystic fibrosis and some forms of muscular dystrophy. Genetic diseases are rare, occurring in roughly one out of every 300 newborn babies. While many people consider genetic diseases undesirable they are natural and unavoidable consequence of human reproduction.
Despite the amazing ability of cells to reproduce themselves, sometimes errors occur. During cellular reproduction, changes in the DNA sequence can occur. This is particularly true during the production of egg and sperm. While most of the changes that occur will not affect the embryo, a few will result in a genetic disease.
The errors that cause genetic disease are located in the DNA itself. Sometimes these errors affect only one gene, such as in Huntington's disease. Sometimes the errors affect whole chromosomes, such as in Down's Syndrome. Such diseases cannot be spread from one individual to another, except from parent to child during reproduction. However, it is important to note that almost all individuals with a genetic disease are born to healthy parents.