The official name of the gene that is affected in Duchene Muscular Dystrophy is Dystrophin and is often called the ‘DMD gene’.
It is the largest known gene in the human genome and spans a massive 2.5 million base pairs and is composed of 79 exons.
Its cytogenetic location is Xp21.2, meaning it is found on the short arm of the X chromosome at position 21.2
Since its discovery, there has been more than 1000 different mutations that occur within the Dystrophin gene that result in the condition.
Duchene Muscular Dystrophy is a result of a genetic abnormality, and in two thirds of cases an affected male inherits the mutation from his mother, who carries an altered copy of the DMD gene.
In the other one-third of cases, Duchene Muscular Dystrophy is a result of spontaneous mutations that are not inherited, but occur after birth.
The majority of associated mutations are ...view middle of the document...
As rumbi has just described the structure of the dystrophin protein is essential in its functionality of binding muscle to its surrounding extracellular matrix. Mutations in the DMD gene dramatically affect the dystrophin protein and ability to carry out its function
Mutations in Exons 2-20 affect the N-terminus in the actin-binding site of molecule, this can be seen as the green region of the diagram and generally result in dystrophin being unable to bind to muscle fibres.
Mutations in Exons 45-55 affect the central rod domain, which is the intermediate region that connects the actin binding region and the region that binds to extracellular matrix.
How is Duchene Muscular Dystrophy inherited?
It is an X linked recessive disease, meaning that the abnormal gene located on the X chromosome causes the phenotype to be expressed in males who are hemizygous for the gene mutation and in females who are homozygous.
This means that in males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the disorder.
Because it is unlikely that females will have two altered copies of this gene, males are affected by X-linked recessive disorders much more frequently than females.
Because males pass on the Y chromosome to their sons, a characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
This diagram describes the inheritance pattern of x linked recessive disease when a carrier mother has children with an unaffected father. , the expected outcome in this scenario
25% chance of a healthy boy
25% chance of a boy with disease
25% chance of a healthy girl
25% chance of a carrier girl without disease
If the father had the disease and the mother is not a carrier, the expected outcomes are:
100% chance of a healthy boy
100% chance of a carrier girl without disease