Abstract
AbstractContinuous exposure of embryonic explants to thymidine‐H3 was used to determine patterns of late‐replicating DNA synthesis, i.e. DNA synthesized during the last quarter of the S period, in chromosomes from different germ layers of developing frog embryos (Rana pipiens). Autoradiographic localization of silver grains over chromosomes 1, 7 and 8, as well as unkaryotyped chromosomes, revealed that patterns of late‐replicating DNA are similar in determined cells that will undergo different pathways of differentiation. In undetermined early gastrula cells and in differentiated tailbud dorsal axial cells (nerve tube, somites and notochord) more sites of DNA synthesis were late‐replicating in chromosomes 1, 7 and 8 and in unkaryotyped chromosomes than in cells of the neural plate‐dorsal mesoderm of neurulae where differentiation is occurring and in neurula endoderm where determination is taking place.
Published Version
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