Correct answer: D). Deletion
Tay-Sachs disease is an autosomal hereditary disease that is known to affect the central nervous system. It results from the mutation caused in the gene that encodes for the beta-hexosaminidase enzyme. It is a lysosomal enzyme that is composed of the beta and alpha polypeptides.
It is caused when both the parents are a carrier, it occurs when a baby is born in absence of hexosaminidase. It affects the nervous system and can change the physical appearance after a few months of the birth.