we have previously shown that a fraction from the nuclei of s phase ( dna-synthesizing ) chinese hamster embryo fibroblasts ( chef/18 cells ) can be obtained that has a number of the enzyme activities required for dna biosynthesis , and can catalyse the incorporation of labelled precursors into dna ( refs 1-4 , also see ref . 8 ) .
C0016030
fibroblasts
C0007634
cells