||African clawed frog Xenopus laevis
||Blow and Laskey, Initiation of DNA replication in nuclei and purified DNA by a cell-free extract of Xenopus eggs. Cell 47:577 1986 p.578 right column top paragraph & p.586 left column 2nd paragraphPubMed ID3779837
||isotope dilution analysis
||P.578 left column: "The endogenous dATP pool in the extract was typically 50µM (45-55µM), as measured by isotope dilution (see Experimental Procedures). Using this figure, the mass of DNA synthesized after 4 hr in Figure 2A represented synthesis of 5 ng DNA/µl extract, equal to the mass of DNA added in the sperm nuclei. This suggests complete replication of the sperm DNA. The size of the dATP pool and the amounts of DNA synthesized were corroborated by the density substitution blotting experiment described in Experimental Procedures." P.586 left column 2nd paragraph: "The endogenous pool of dATP in the extracts was measured by performing parallel incubations under conditions for optimum synthesis, with varying concentrations of exogenous dATP and constant concentrations of [α-32P]dATP and [3H]dTTP. Endogenous dATP concentrations were calculated assuming the following relation: [32P] incorporated × (exogenous dATP + endogenous dATP)=constant × [3H] incorporated. This gave an endogenous dATP pool of 50µM (45-55µM)."