Review Question - QID 212479

A 21-year-old woman makes an appointment with a geneticist for counseling after finding out that she is pregnant with her first child. Specifically, she is worried because she has a 13-year-old brother who has been experiencing progressive muscle weakness since childhood. He is now attending middle school and uses a power wheelchair to get around. He also requires bilateral leg braces as well as a thoracolumbar brace because he is unable to hold his body upright in the wheelchair without restraints. She says that she remembers her brother using the method shown in Figure A to stand up when he was still able to walk. Though she is very close to her brother, she is worried that her child will also have the same disorder. She does not yet know the sex of the child, and her husband does not have the mutated gene. What is the probability that her child will be affected by this disorder?