1.   And the third gene was one that causes the cell to make an enzyme called telomerase.

2.   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.

3.   One of the viral genes instructs the cells to make an enzyme, thymidine kinase, that normally would be completely innocuous.

4.   Only when this protein has been pried loose from the DNA can bacteria make the enzymes they need to digest lactose.

5.   Some of the newly discovered genes appear to make enzymes that protect it from being digested by stomach acids.

6.   The only information it carries are the instructions for making the enzyme it needs to cleave DNA.