a genetic disease in which the body is unable to get rid of a fatty substance called ganglioside so that it builds up in the brain, causing the nerves to stop working properly and eventually leading to death, usually before the age of three

For a child to have Tay-Sachs Disease, both parents must have the defective gene responsible. 只有当父母都携带有缺陷的相关基因时，他们的孩子才会罹患家族黑蒙性白痴病。