What are the genetics of sma?

Autosomal recessive: A defect in the smn1 gene is what is inherited. Someone has to get 2 copies of this defective gene (one from mom and one from dad) to have sma. If someone only has one copy of the defective-they are a carrier and can pass on that gene to their offspring.

SMA: Spinal muscular atrophy (sma) is an autosomal recessive disease caused by a genetic defect in the smn1 gene that codes smn, a protein widely expressed in all eukaryotic cells.The overall incidence of sma, of all types and across all ethnic groups, is in the range of 1 per 10, 000 individuals; the gene frequency is thus around 1:100, therefore, approximately one in 50 persons are carriers.

More than one type: Spinal muscular atrophy of infants, before the gene was identified, was called Werdnig-Hoffman disease. Pitiful-we always looked at the tongues of floppy babies hoping it wasn't fasciculating. No treatment, breathing muscles progressively weakened, resulting in suffocation. 1 chance in 4 of recurrence-maybe. 2% were new mutations. Kugleberg-Weilander disease had onset after 12 mo. Now 10 forms.

Spinal muscular atro: There are different forms of spinal muscular atrophy (SMA), which can result from mutations in the following genes: SMN1, UBA1, DYNC1H1, and VAPB. Having added copies of the SMN2 gene may impact the severity of SMA. (NIH, Genetics Home Reference, Spinal Muscular Atrophy)