1.   But it was sometimes hard to procure enough calf stomachs, so the enzyme is now made by bacteria or yeast with the calf enzyme gene.

2.   If the enzyme gene could be placed inside a tumor cell, then it might make the tumor susceptible to the drug, he reasoned.

3.   Doctors in Italy and Israel cured the children with injections of bone marrow stem cells that had been altered to contain the missing enzyme gene.

4.   The treatment consisted of injections of bone marrow stem cells that were altered to contain the missing enzyme gene.