▁base ▁pair ▁addition ▁( T AT C ) ▁in ▁ex on ▁ 1 1 ▁of ▁the ▁H ex ▁A ▁gene . ▁This ▁insert ion ▁leads ▁to ▁an ▁early ▁stop ▁cod on , ▁which ▁causes ▁the ▁H ex ▁A ▁def ic iency . ▁ ▁Children ▁born ▁with ▁T ay – S ach s ▁usually ▁die ▁between ▁two ▁and ▁six ▁years ▁of ▁age ▁from ▁asp iration ▁and ▁p neum onia . ▁T ay – S ach s ▁causes ▁c ere br al ▁deg ener ation ▁and ▁blind ness . ▁Pat ients ▁also ▁experience ▁fla cc id ▁extrem ities ▁and ▁se iz ures . ▁There ▁is ▁no ▁c ure ▁for ▁T ay – S ach s ▁disease . ▁ ▁Gene ▁Ther ap ies ▁for ▁T ay - S ach s ▁ ▁The ▁H EX A ▁gene ▁is ▁a ▁protein ▁encoding ▁gene ▁that ▁codes ▁for ▁the ▁l ys os om al ▁en zym e ▁beta - hex os amin id ase . ▁This ▁en zym e , ▁combined ▁with ▁the ▁G M 2 ▁activ ator ▁protein , ▁is ▁responsible ▁for ▁the ▁break down ▁of ▁gang li os ide ▁G M 2 ▁within ▁the ▁l ys os ome . ▁De fect s ▁in ▁the ▁H EX A ▁gene , ▁however , ▁prevent ▁this ▁de grad ation , ▁leading ▁to ▁a ▁bu il dup ▁of ▁to x ins ▁in ▁brain ▁and ▁sp inal ▁cord ▁cells . ▁This ▁fatal ▁gen etic ▁dis order ▁is ▁called ▁T ay - S ach s ▁disease . ▁Because ▁the ▁T ay - S ach