Tay Sachs....?

Is this disease cause by a dominant allele , recessive alleles, extra chromosome or is is sex linked?
What does it do the the affected person?

I think it's recessive alleles. Both parents must be a carrier.
Infants with Tay-Sachs disease appear to develop normally for the first six months of life. Then, as nerve cells become distended with gangliosides, a relentless deterioration of mental and physical abilities occurs. The child becomes blind, deaf, and unable to swallow. Muscles begin to atrophy and paralysis sets in. Death usually occurs before the age of 4 or 5.
Extremely rare, Juvenile Tay-Sachs disease usually presents itself in children between 2 and 10 years of age. They develop cognitive, motor, speech difficulties (dysarthria), swallowing difficulties (dysphagia), unsteadiness of gait (ataxia), and spasticity. Patients with Juvenile TSD usually die between 5鈥?5 years.
A rare form of the disorder, known as Adult Onset Tay-Sachs disease or Late Onset Tay-Sachs disease (LOTS), occurs in patients in their 20s and early 30s. LOTS is frequently misdiagnosed, and is usually non-fatal. It is characterized by unsteadiness of gait and progressive neurological deterioration. Symptoms of LOTS, which present in adolescence or early adulthood, include speech and swallowing difficulties, unsteadiness of gait, spasticity, cognitive decline, and psychiatric illness, particularly schizophrenic-like psychosis. Patients with LOTS frequently become full-time wheelchair users in adulthood, but many live full adult lives if psychiatric and physical difficulties are accommodated. Psychiatric symptoms and seizures can be controlled with medications.

Autosomal recessive

Tay Sachs is a very rare genetic disorder where there is an insufficient production of hexosaminidase A (HEXA). It causes fatty material to build up in nerve cells, predominantly in the brain.

This in turn leads to impaired function of the nerve cells, difficulties with and finally inability of:
walking
talking
swallowing
coordinating movements of arms