Inheritance and Genetics of Spinal Muscular Atrophy
Spinal Muscular Atrophy Genetics: Book Excerpts
Spinal Muscular Atrophy: Genetics Information
Genetics of Spinal Muscular Atrophy:
Expression of the disease requires mutation of both alleles of the survival motor neuron gene (SMN1) found on chromosome 5, making SMA an autosomal recessive disorder. Typically, the mutations are caused by a deletion within SMN1, or when the SMN1 gene is replaced by an almost identical gene called SMN2, also located on chromosome 5. Both SMN1 and SMN2 code for identical proteins, but the SMN1 gene produces the full-size protein, whereas the SMN2 gene produces truncated versions of the protein, and a small amount of the full-size protein. Deletions within both copies of the SMN1 gene results in type I SMA, whereas the milder forms of SMA usually occur when SMN1 is replaced by SMN2, increasing the number of copies of SMN2. The more SMN2 genes an affected individual has, the more full-length protein will be produced, and the milder the resultant form of the disease. The protein encoded by SMN1 and SMN2, which is known to play a crucial role in the production of mRNA, is expressed throughout the body, but is found in especially high levels within the spinal motor neurons.
(Source: Genes and Disease by the National Center for Biotechnology)
About inheritance and genetics:
Inheritance of Spinal Muscular Atrophy refers to whether the condition is inherited
from your parents or "runs" in families.
The level of inheritance of a condition depends
on how important genetics are to the disease.
Strongly genetic diseases are usually inherited,
partially genetic diseases are sometimes inherited,
and non-genetic diseases are not inherited.
For general information, see Introduction to Genetics.
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