What is the cause of duchenne muscular dystrophy (dmd)?

Duchenne muscular dystrophy (DMD) is a kind of muscular dystrophy characterized by severe muscle loss. It is a X-linked recessive disorder. It begins by muscle weakness and most patients lose walking ability by the age of 12. Some may also suffer from intellectual disability.

The cause for DMD is a mutation that occurs at dystrophin gene located on X chromosome. Dystrophin connects muscle fiber cytoskeleton to basal lamina. In absence of dystrophin, excess calcium enters the sarcolemma leading to stress induced reactive oxygen species production. Sarcolemma is damaged and eventually cell death occurs. Muscle fibers die by necrosis and are replaced by adipose and connective tissue.

≅200-130 milions years ago pangea splited in 2 continents

the denominator has a very specific role.