“This is a disease caused by a chromosomal defect in utero. It is a structural abnormality in the chromosome that causes nerve cells in your body to become inflamed and not function properly.”
“This is an autoimmune disease in which antibodies attack the muscles and muscle atrophy occurs. The muscles will become weak and begin to waste.”
“This is an autoimmune disease in which antibodies destroy acetylcholine at the neuromuscular junction. This prevents your muscles from contracting normally.”
“This is a hereditary condition caused by a recessive gene. It causes nervous tissue to be broken down, and damage occurs to the brain and spinal cord.”
Number 3 is correct.
Rationale: Myasthenia gravis is an autoimmune disease in which antibodies destroy acetylcholine at the neuromuscular junction, causing muscles to be unable to contract normally. The muscles become weak and fatigued. While muscle wasting can occur in severe instances, it is not indicative of the condition. The brain and spinal cord are not damaged from myasthenia gravis.