SMN1 Deletion Mutations and Conversion Mutations

Approximately 94% of individuals with clinically typical SMA lack both copies of SMN1 exon 7.[7] Loss of SMN1 exon 7 can occur by a large deletion, typically including the whole gene, or by conversion to SMN2 exon 7. Absence of the SMN1 exon 7 sequence indicates a functional or a de facto absence of the SMN1 gene.

Most converted genes from SMN1 to SMN2 had SMN2 sequences in all of the polymorphic nucleotides except for the SMN1 sequence in exon 8.[8] A half of the hybrid SMN1/SMN2 genes had a single Ag1-CA/C212 haplotype, suggesting that these hybrid SMN alleles had a common origin.[8] Other variants of hybrid SMN genes are rarely present. Considering increased number of SMN2 copies in mild SMA patients in the absence of SMN1 exon 7, gene conversion from SMN1 to SMN2 is a more likely hypothesis than unequal recombination and intrachromosomal deletion.[8] There is also evidence of gene conversion from SMN2 to SMN1.[9]

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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