B. 50% – Explanation
Duchenne muscular dystrophy is a X-linked recessive disorder. Since the first child is
affected, it means that the mother is a carrier. Since the sex of the second child is
known and noted to be male, the chances of child being affected are 50%.
affected, it means that the mother is a carrier. Since the sex of the second child is
known and noted to be male, the chances of child being affected are 50%.
Other notable X-linked recessive disorders are
- HaemophiliaA and B
- Red-green colorblindness
