Tay-Sachs disease is a rare inherited disorder that progressively destroys nerve cells (neurons) in the brain and spinal cord. The most common form of Tay-Sachs disease becomes apparent in infancy. Infants with this disorder typically appear normal until the age of 3 to 6 months, when their development slows and muscles used for movement weaken. Affected infants lose motor skills such as turning over, sitting, and crawling. They also develop an exaggerated startle reaction to loud noises. As the disease progresses, children with Tay-Sachs disease experience seizures, vision and hearing loss, intellectual disability, and paralysis. Children with this severe infantile form of Tay-Sachs disease usually live only into early childhood.
Tay-Sachs disease has been identified in the HEXA gene. One of the known mutations can eliminate the activity of the enzyme, which prevents the enzyme from breaking down a fatty substance. As a result, this substance builds up to toxic levels, particularly in nerve cells in the brain and spinal cord. Progressive damage caused by the buildup of the fatty substance leads to the destruction of these cells, which causes the signs and symptoms of Tay-Sachs disease
Riley was diagnosed with Tay-sachs, which he inherited from both his parents. Riley received a mutated copy of the gene from his mom and a mutated copy from his dad. Neither of his parents has Tay Sachs disease. You must have two copies of the mutated gene in order to develop Tay Sachs disease.

What happened to the HEXA gene of Riley's parents?

What effect did the inherited mutated genes have on Riley at the cellular level?

Is this mutation beneficial, harmful, or neutral to Riley? Defend your answer.

Is this mutation physically beneficial, harmful, or neutral to Riley's parents? Defend your answer.

Does the Tay Sachs mutation increase or decrease genetic diversity? Explain your answer.