Deoxyribonucleoside triphosphate pools in vitamin B-12-deficient Euglenagracilis.

The size of the deoxyribonucleoside triphosphate pools of vitamin B-12-deficient cells of Euglena gracilis, and of vitamin B-12-deficient cells repleted with the vitamin, were measured. We found that the pools were very small, if they exist at all, in deficient cells but expand rapidly with the addition of the vitamin. The sizes of the pools decrease when DNA synthesis is completed, and are very small when the cells begin to divide.