please, do not use information you need like that from an open forum like this. i'm sure many people here could answer some of those questions you've asked (even i can after taking genetics), but the reliability of that information would always have to get confirmed by another source such as geneticist/physician or a legitimate online source. if u need a first person source, go to a hospital and talk to a doctor. a more appropriate question for btf would be to ask for anyone that has experienced tay sachs (thru friends, family, work, etc) and to describe it that way.

This mite help you with Tay Sachs disease, its a genetic deficiencies of sphingolipid, in Tay sachs there is enzyme called Hexosaminidase A, which is missing and that leads to accumulating of Ganglioside GM2 in your body, and symptoms are : cherry red spots in macula, Blindness, Psychomotor retardation, death usually <2 yrs and its very common in Jewish people. i hope this info will help you.