The present invention relates to the discovery of the human survival motor-neuron gene or SMD gene, which is a chromosome 5-SMA (Spinal Muscular Atrophy) determining gene. The present invention further relates to the nucleotide sequence encoding the SMN gene and corresponding amino acid sequence, a vector containing the gene encoding the SMN protein or a DNA sequence corresponding to the gene and transformant strains containing the SMN gene or a DNA sequence corresponding to the gene.