Appearance of DNA polymerase activities during early development of Xenopus laevis

Extracts of large oocytes of Xenopus laevis contain high levels of one major DNA polymerase activity. After maturation into eggs, the overall level of DNA polymerase activity in extracts increases fourfold and a second major activity appears on Sephadex G-200 or DEAE cellulose columns. Although intense DNA synthesis occurs as the number of cells increase from one to over 100,000, no further increases in the level of either DNA polymerase activity are observed in cleavage, gastrula or early neurula stage embryos. In extracts of late neurulae or hatched embryos, however, a third major DNA polymerase activity appears coincident with an increase in the ability of the extracts to utilise native DNA templates in vitro.