Many different defects in a particular gene can occur, and, of course, defects can occur in many different genes. All genes are inherited, half coming from a child's mother, the other half from the father. Flaws in genes can be inherited along with the parents' genes, although they can also occur for the first time in a child. Scientists use the term spontaneous mutation when this happens. Doctors use the term familial for a disease that occurs with a family history and sporadic when there's no family history.
Sporadic diseases can nevertheless stem from gene flaws.
Genes are found in virtually every cell in the body, including muscle cells, on structures called chromosomes. Each person has 46 chromosomes. One chromosome out of each matched pair is inherited from the mother, the other from the father. The remaining two chromosomes, the X and Y chromosomes, determine whether the individual is male or female. A male has an X chromosome, which he inherits from his mother, and a Y chromosome, which he inherits from his father.