21.   When cells Harley and Shay had altered began producing telomerase, the effect was remarkable.

22.   When these cells begin to grow out of control, a cancer develops called a melanoma.

23.   When the gene is disrupted by a mutation, however, the safety brake is released, and the cells can begin their manic descent into cancer.

24.   Within three weeks, the cells began producing proteins found only in bone.

25.   With no blood, and the oxygen it carries, brain cells begin to die.

26.   Within several hours, brain cells begin to die.

27.   Cancer is a disease in which individual cells begin by prospering selfishly at the expense of their neighbours.

28.   In tests on dogs with fractures, the scientists inserted the sponges into the damaged area, and bone cells began to grow into it, Bonadio said.

29.   Once in the brain, the modified cells began making NGF.

30.   Those cells begin to crowd out normal, healthy cells in the marrow.