Sarah and Brianna

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Where on Chromosome is Problem?

Type 1 is found in the DMPK gene, and Type 2 is found in the CNBP gene. A short segment of abnormal DNA is repeated several times creating a "unstable region of the gene". It's found on Chromosome 19. A normal person will have 5-35 CTG repeats, but a person with myotonic dystrophy, the repeat is unstable and expands. The expansion is anywhere from 50 repeats to several thousands. The severity of the disorder depends on how many repeats there are.

Dystrophy myotonic-protein kinase (DMPK)

What Is the Problem?

The expanded sections of DNA suggest to have molecular consequences on a variety of cellular processes. Research has not yet revealed how this mutation leads to the disease, but theories suggest that the expansion negatively affects the surrounding genes. After transcription, the long CTG template creates the abnormality of a lengthy CUG segment in the mutant mRNA. These become concentrated in nuclear foci, causing major disruption in RNA-binding and resulting in the observed effects.

What is the Prognosis?

Myotonic dystrophy causes muscle weakness, difficulty relaxing muscles (after they've been contracted), heart problems, and breathing problems. There is currently no cure for Myotonic Dystrophy, although ankle and leg braces can help as it gets worse, and medication can even lessen the effects. Myotonic dystrophy doesn't always result in death, but sometimes the medical conditions are so severe that they result in death.

Cite Your Sources

Myotonic Dystrophy Support Group

Human Molecular Genetics

Overview: Myotonic Muscular Dystrophy