Muscular dystrophy, a muscle-wasting disorder, is caused by mutations in the DMD gene.  The DMD gene codes for a protein called dystrophin that is necessary for muscle cells to maintain their shape.  When this protein is missing, muscle cells literally burst as material from outside the cell membrane leaks in, raising cell pressure.  Mutations in the DMD gene can cause Duchenne muscular dystrophy or its milder form, Becker muscular dystrophy.  People who are born with muscular dystrophy experience gradual, severe muscle loss and become unable to walk by age 10.  Sequencing the DMD gene can reveal who will develop muscular dystrophy.