The HEXA gene codes for a protein that breaks down and recycles toxic substances in our brain and spinal cord. Mutations in the HEXA gene lead to Tay-Sachs disease. This is a disorder in which the level of toxic substances builds in the brain and spinal cord, leading to severe brain damage and eventually death. In many patients with Tay-Sachs, an insertion of four base pairs is seen in the HEXA gene. In general terms, explain how this insertion impacts the protein that is produced.