Neither parent may be aware of it. If both are carriers of the same gene, all children risk manifestation of the inheritance. Chances are that one in four that they will be non-carriers of the gene, similarly one in four that they will suffer the disease or disorder. X - Linked inheritance results from an abnormal gene on one of the X chromosomes. A mother with the abnormal gene on one X chromosome has a 50 percent chance of passing it on to a male child.
Females normally have two X chromosomes.
These are sex determining chromosomes. In such case each son has an even risk of inheriting the gene because he inherits one of the X chromosomes from his mother and the Y chromosome from his father. A daughter may inherit either of the mother's X chromosomes and risks a 50 percent chance that she will be a carrier of the estimated 250 disorders or diseases. Sons cannot be carriers. Chromosome Disorders can occur when either the egg or sperm are forming.