The 23rd pair consists of the sex chromosomes. Most often, genes produce normal traits. Sometimes, however, a gene becomes altered from its original form. Although researchers know that mutations occur, the reasons for their occurrence is not completely understood. Some mutations are not harmful, but most often a mutant gene functions improperly and causes a disorder, malfunction, or malformation within the body.
Mutations can occur in any generation.
If a spontaneous mutation occurs, it is then possible for a child to be the first family member to get a genetic disorder such as Marfan syndrome, even though both parents are normal. The result can be a disease, such as cystic fibrosis. For most locations, each individual possesses two alleles, one derived from each parent. Therefore, if one parent contributes the Marfan gene and one parent contributes a normal gene, the child will inherit the Marfan disorder. It is important to remember that parents have no control over which genes they pass on to their children, and, therefore, should not feel at fault if one of their children inherits a disorder such as the Marfan syndrome.