MOLECULAR GENETICS

#310200) is an X-linked recessive inherited muscle-wasting disease characterised primarily by progressive weakness and atrophy of the skeletal and cardiac muscle. DMD patients are typically wheelchair-bound by 12 years of age and die in their late teens or early twenties of respiratory failure. It is one of the most common Mendelian disorders, occurring in all population groups with a birth prevalence of approximately 1/3 500 males. The disease gene, DMD, linked to chromosome Xp21.2, was one of the first genes to be isolated by positional cloning,[1] and the deficient product in affected boys was then identified as the protein dystrophin. [2] Dystrophin localises to the cell membrane in muscle cells and binds the protein actin, in this way forming part of the protein complex which links the cytoskeleton with the cell membrane. The gene is extremely large, spanning 2 400 kb of genomic DNA and comprisin