i need help on my biology project?
i need to know this followings to do my project
3) who gets the disorder
4) what effect does mutation have
for Sex-linked Musculary Dystrophy....
- 1 decade agoFavorite Answer
Sex-linked muscular dystrophies include several inherited muscle disorders that result in significant progressive muscle weakness (proximal (nearer the abdomen/thorax) more and earlier than distal (knees, wrists...) muscles), diminished joint flexibility (contractures) and ultimately, decreased life span. Duchenne Muscular Dystrophy (DMD) is by far the most common of these disorders, followed by Becker and Emery-Dreifuss muscular dystrophy. Accordingly, the answers below refer specifically to DMD, though the other muscular dystrophies are similar.
Unless a sibling is affected, DMD is usually discovered when the child begins to walk. Early signs include delayed motor milestones (e.g. starts to walk ~18 months of age), gait abnormalities (wide, waddling stance, pelvis tilted forward). Frequent falls are common, as is characteristic weakness of the hip flexors (the muscles that raise the thigh up & forward). Mild to moderate mental deficits are also common. As contractures and upper limb involvement progress, the child usually becomes wheelchair-bound by age 7-13. Other common abnormalities include enlarged tongue and calf muscles, and diminished reflexes in the knee and upper extremities.
DMD affects about 1 in 3500 males born globally. The second most common muscular dystrophy (Becker's M.D.) affects about 1 in 30,000 males.
Mutation of the X-chromosome (p21 region for Becker and DMD; q28 for Emery-Dreifuss) affects the production of dystrophin and other proteins that maintain the integrity of muscle cell walls. Muscle cell leakage and damage causes the progressive signs of these disorders.
As for cause, this and other X-linked disorders can be carried by females, as they have two X chromosomes. If a male inherits a defective copy of the X-chromosome, he will typically inherit the disorder.
Prednisone is the only medical treatment with proven benefit. Other immunosuppressive drugs such as azathioprine and cyclosporine are being investigated. A novel product candidate from a New Jersey-based company (PTC124 from PTC Therapeutics) is in Phase II clinical trials for DMD as well as cystic fibrosis. Somatic gene therapy is also being investigated, with the objective of creating sufficient normal muscle function to overcome the inherited deficiencies. Physical and surgical therapy is aimed at correcting/minimizing the deformities of the disease. Despite these measures, affected people usually die in their third decade of life, often as a result of respiratory infection that overwhelms the progressively weakened cardiorespiratory system.
Other info-Medical technology now enables detection of DMD as early as the first trimester. However, this presents several ethical dilemmas to parents & physicians...given the choice, would a mom to-be choose to be tested? If disease is detected, would she choose to end a pregnancy that would otherwise (likely) result in a son who would require extensive medical care, and who would probably die before she retires? Should every mom to-be have mandatory screening?Source(s): Medscape & my medical education.
- ?Lv 61 decade ago
read the sitesSource(s): http://www.nature.com/scitable/topicpage/Sex-%E2%8... http://en.wikipedia.org/wiki/Muscular_%E2%80%8Bdys...