Genetics

If a woman is a carrier for X-ALD with the genotype X^AX^a  (where ^A represents a normal gene and ^a represents a gene for ALD) marries a man with the genotype X^AY, they have a 50% chance of having a carrier daughter, a 50% chance of having an unaffected daughter, a 50% chance of having a son with X-ALD, and a 50% chance of having an unaffected son. This scenario is displayed on Diagram 1 below. In a different case, an unaffected woman with the genotype X^AX^A marries a man with X-ALD and the genotype X^aY; if they were to have children, all of the daughters would be carriers (since he is only able to pass on a defected X chromosome to his daughters) and all sons would be unaffected (since he is only able to pass on a Y chromosome to his sons). This situation is shown on Diagram 2 pictured below.

Diagram 1

Diagram 2