Base Composition of Normal and Megaloblastic Bone Marrow DNA

PARRY has speculated that in megaloblastic anaemia, deficiency of folate or vitamin B₁₂ may mean that a population of cells is formed in the marrow containing DNA with subnormal amounts of thymidine, so accounting for some of the abnormalities of megaloblastic erythropoiesis¹. We have therefore determined the base composition of DNA from normal and megaloblastic cells and have also measured the amounts of 5-methylcytosine^2,3 present in these DNA preparations, as vitamin B₁₂ and folate are known to be concerned in many methylation reactions in man⁴ and could be directly or indirectly concerned in the formation of 5-methylcytosine.