SMN1
Survival of motor neuron 1 (''SMN1''), also known as component of gems 1 or ''GEMIN1'', is a gene that encodes the SMN protein in humans. Gene ''SMN1'' is the telomeric copy of the gene encoding the SMN protein; the centromeric copy is termed '' SMN2''. ''SMN1'' and ''SMN2'' are part of a 500  kbp inverted duplication on chromosome 5q13. This duplicated region contains at least four genes and repetitive elements which make it prone to rearrangements and deletions. The repetitiveness and complexity of the sequence have also caused difficulty in determining the organization of this genomic region. ''SMN1'' and ''SMN2'' are nearly identical and encode the same protein. The critical sequence difference between the two is a single nucleotide in exon 7 which is thought to be an exon splice enhancer. It is thought that gene conversion events may involve the two genes, leading to varying copy numbers of each gene. Clinical significance Mutations in ''SMN1'' are associated w ...
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Spinal Muscular Atrophy
Spinal muscular atrophy (SMA) is a rare neuromuscular disorder that results in the loss of motor neurons and progressive muscle wasting. It is usually diagnosed in infancy or early childhood and if left untreated it is the most common genetic cause of infant death. It may also appear later in life and then have a milder course of the disease. The common feature is progressive weakness of voluntary muscles, with arm, leg and respiratory muscles being affected first. Associated problems may include poor head control, difficulties swallowing, scoliosis, and joint contractures. The age of onset and the severity of symptoms form the basis of the traditional classification of spinal muscular atrophy into a number of types. Spinal muscular atrophy is due to an abnormality (mutation) in the '' SMN1'' gene which encodes SMN, a protein necessary for survival of motor neurons. Loss of these