Duchenne Muscular Dystrophy Concepts

What type of genetic mutation causes Duchenne Muscular Dystrophy (DMD)?

• Autosomal dominant mutation

• X-linked recessive mutation

• Mitochondrial DNA mutation

• Somatic cell mutation

What are healthy muscle cells also known as?

• Neurons

• Osteocytes

• Myocytes

• Adipocytes

What protein, essential for muscle contraction, is coded by genes in myocyte nuclei?

• Collagen

• Myosin

• Actin

• Dystrophin

What is the primary function of dystrophin in muscle cells?

• To produce energy for muscle contraction.

• To transport oxygen to muscle tissues.

• To connect the dystroglycan complex to the actin cytoskeleton, acting as a stiffener and shock absorber.

• To initiate nerve impulses for muscle movement.

What happens to dystrophin in individuals with Duchenne Muscular Dystrophy (DMD)?

• It is overproduced, leading to muscle stiffness.

• It is made in very small amounts, is damaged, or is not made at all.

• It mutates into a different, non-functional protein.

• It is only produced in non-essential muscles.

What is a direct consequence of the lack of dystrophin in muscle cells?

• Increased muscle elasticity.

• Muscles tear easily with contractions.

• Enhanced muscle regeneration.

• Reduced calcium levels in the myocyte cytoplasm.

Why does the leakage of extracellular calcium into the myocyte cytoplasm contribute to muscle weakness in DMD?

• It directly inhibits muscle contraction.

• It causes the muscle cells to swell and burst.

• It activates proteases that destroy healthy proteins.

• It prevents the formation of new muscle fibers.

What is the role of proteases in the context of Duchenne Muscular Dystrophy (DMD) when activated by calcium?

• They help repair damaged muscle fibers.

• They destroy old proteins but spare healthy ones.

• They destroy both old/worn-out proteins and healthy proteins like the dystroglycan complex.

• They convert calcium into an energy source for muscles.

Why are creatine kinase (CK) levels high in boys with Duchenne Muscular Dystrophy (DMD)?

• CK is overproduced by healthy muscle cells.

• CK leaks out of torn myocytes due to muscle damage.

• CK is a byproduct of fat and fibrotic tissue replacement.

• CK is actively secreted by the immune system in response to the disease.

Besides skeletal muscles, which other muscles are affected by Duchenne Muscular Dystrophy (DMD)?

• Smooth muscles in the digestive system.

• Muscles of the eye.

• Heart and diaphragmatic muscle.

• Muscles responsible for hearing.