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Tay-Sachs is a rare inherited disease that is caused by a mutation in the HEXA gene.This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The HEXA gene provides the information for making an enzyme called beta-hexosaminidase A, which plays a critical role in the brain and spinal cord. The mutation prevent the enzyme from doing its job which is to  break down a fatty substance called GM2 ganglioside. Because of this, the nerve cells are progressively destroyed in the brain and the spinal cord. Typically, babies do not survive past the age of 4, however do not start showing symptoms until 3-6 months.