When there is no functioning dystrophin, muscle cells get easily damaged due to repeated contractions and relaxations. Eventually, these weakened muscle cells die, leading to the characteristic muscular deterioration linked to DMD. With progress in the disease, individuals generally males get confined to a wheelchair and eventually develop heart failure because of weakening and dead cardiac muscle. DMD can be caused by several thousand possible mutations. Most of them are deletions, missing DNA, which"CRISPR-Cas9 heals disease in mice ( mouse)"