A 14C- and 3H-thymidine double labeling technique in the study of cell proliferation in Tradescantia root tips

Abstract

A double labeling technique is described in which a cell population is briefly labeled with ³H-thymidine and then labeled again after a short period of time with ¹⁴C-thymidine. Two labeled populations of cells may be resolved autoradiographically, viz. those labeled only with ³H and all cells labeled with ¹⁴C. The cells labeled only with ³H will have left DNA synthesis during the interval between treatments and hence, their numbers will be proportional to the length of time between treatments. Likewise the numbers of all cells labeled with ¹⁴C will be proportional to the duration of DNA synthesis. If a representative sample of such a population is scored for these two groups of labeled cells, the length of DNA synthesis (S) and mitosis may be immediately calculated. By increasing the time between the first and the second labels, the duration of the pre- and post-DNA synthetic periods (G₁ and G₂) may also be determined. Five cell population types are discussed and equations relating to the double-labeling of these populations are presented.