A male has one X and one Y sex chromosome, and a female has two X chromosomes. A sex-linked disorder is caused by a mutation in a gene on the X chromosome. As males only have one copy of each gene on the X chromosome, they'll be affected if one of those genes is mutated.
As females have two copies of the X chromosome, they're less likely to develop an X-linked condition, because the normal copy of the chromosome can usually cover for mask the altered version.
Females can still be affected by X-linked disorders, but the condition is usually less severe than when the gene alteration is present in an affected male. Spontaneous gene mutations can occasionally cause MD. This is where the genes mutate for no apparent reason, changing the way the cells function.
Spontaneous gene mutations can cause MD to develop in people who don't have a family history of the condition. Another way a child with no family history can be affected is when the condition is recessive. The gene mutations may have been present on both sides of the family for many generations but may not have affected anyone until a child inherited a copy of the altered gene from both parents.
Genes are units of DNA that determine many of your body's characteristics, such as the colour of your hair and eyes. Genes are found on strands called chromosomes. Each cell in the body contains 23 pairs of chromosomes, which carry the genes you inherit from your parents.
There are two possible explanations. The first is that the genetic mutation leading to DMD may have existed in the females of a family for some generations without anyone knowing. Perhaps no male children were born with the disease, or, even if a boy in an earlier generation was affected, relatives may not have known what disease he had.
A man with DMD cannot pass the flawed gene to his sons because he gives a son a Y chromosome, not an X. They will then be carriers, and each of their sons will have a 50 percent chance of developing the disease and so on. A good way to find out more about the inheritance pattern in your family is to talk to your MDA Care Center physician or a genetic counselor.
When a girl inherits a flawed dystrophin gene from one parent, she usually also gets a healthy dystrophin gene from her other parent, giving her enough of the protein to protect her from the disease. Males who inherit the mutation get the disease because they have no second dystrophin gene to make up for the faulty one. Early in the embryonic development of a female, either the X chromosome from the mother maternal X or the one from the father paternal X is inactivated in each cell.
Chromosomes become inactivated at random. In each cell, there is a 50 percent chance that either the maternal or paternal X chromosome will be inactivated, with the other left active.
Usually, girls do not experience the full effects of DMD the way boys do, although they still have symptoms of muscle weakness. A minority of females with the mutation, called manifesting carriers , have some signs and symptoms of DMD. For these women, the dystrophin deficiency may result in weaker muscles in the back, legs, and arms that fatigue easily. Manifesting carriers may have heart problems, which can show up as shortness of breath or an inability to do moderate exercise.
The heart problems, if untreated, can be quite serious, even life-threatening. In very rare instances, a girl may lack a second X chromosome entirely, or her second X may have sustained serious damage. In these cases, she makes little or no dystrophin depending on the type of dystrophin mutation , and she develops a dystrophinopathy just as a boy would. A female relative of a boy with DMD can get a full range of diagnostic tests to determine her carrier status.
There is currently no cure, but certain physical and medical treatments can improve symptoms and slow the progression. Muscular dystrophy is a group of over 30 conditions that lead to muscle weakness and degeneration. As the condition progresses, it becomes harder to move.
In some cases, it can affect breathing and heart function, leading to life-threatening complications. Depending on the type and severity, the effects can be mild, progressing slowly over a normal lifespan, there may be moderate disability, or it can be fatal.
The symptoms of Becker muscular dystrophy are similar but tend start in the mid-twenties or later, are milder, and progress more slowly. Currently, there is no cure for muscular dystrophy. Medications and various therapies help slow the progression of the disease and keep the patient mobile for the longest possible time.
Muscular dystrophy is caused by mutations on the X chromosome. Each version of muscular dystrophy is due to a different set of mutations, but all prevent the body from producing dystrophin. Dystrophin is a protein essential for building and repairing muscles. Duchenne muscular dystrophy is caused by specific mutations in the gene that encodes the cytoskeletal protein dystrophin. Dystrophin makes up just 0. Dystrophin is part of an incredibly complex group of proteins that allow muscles to work correctly.
The protein helps anchor various components within muscle cells together and links them all to the sarcolemma — the outer membrane. If dystrophin is absent or deformed, this process does not work correctly, and disruptions occur in the outer membrane.
This weakens the muscles and can also actively damage the muscle cells themselves. In Duchenne muscular dystrophy, dystrophin is almost totally absent; the less dystrophin that is produced, the worse the symptoms and etiology of the disease.
In Becker muscular dystrophy, there is a reduction in the amount or size of the dystrophin protein. The gene coding for dystrophin is the largest known gene in humans.
More than 1, mutations in this gene have been identified in Duchenne and Becker muscular dystrophy. Duchenne muscular dystrophy can lead to life-threatening complications, such as breathing difficulties and heart problems. In the past, people with this condition did not usually survive beyond their 20s, but progress is improving the outlook.
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