An electron microscope study of chromosomal DNA replication in different eukaryotic systems

We have carried out an electron microscope study of replication intermediates in chromosomal DNA from V. faba root tips; D. melanogaster, X. laevis and chick at different developmental stages; goldfish and brown trout germinal and somatic tissues; regenerating rat liver; Chinese hamster and X. laevis cultured cells. Clusters of small eyes (microbubbles, 100-300 base pairs) and single-stranded DNA molecules have been observed in all the systems analysed, whereas long replication eyes (macrobubbles) were present only in early cleavage embryos of D. melanogaster. The relative frequency of these structures has been compared with similar data from the literature and their relevance as replication intermediates discussed. © 1982.