Final answer:
Muscular dystrophy signifies the gradual weakening and degeneration of muscle tissue due to defective proteins affecting the skeletal muscles, leading to functional impairments such as difficulty in walking.
Step-by-step explanation:
Muscular dystrophy is a genetic disorder that is characterized by the progressive weakening of muscle tissue, specifically skeletal muscles, due to defective proteins. Over time, this leads to the death of muscle cells and tissues, significantly reducing muscle mass and function. Duchenne muscular dystrophy (DMD), a type of muscular dystrophy, is caused by a deficiency of dystrophin, which is essential for maintaining muscle cell integrity.
Lack of dystrophin leads to damage of the sarcolemma during muscle contractions, followed by cellular damage and muscle fiber degradation. This progressively impairs motor abilities, often beginning with difficulty in walking during childhood.
The correct answer to the question would be: d. weakening of muscle tissue.