Differential Staining of Late Replicating DNA-Rich Regions inAllium CepaChromosomes

SUMMARYBy using BrdU-dye methodology, the location of late replicating DNA and the degree of coincidence between it and heterochromatic regions (C-bands) have been determined in Allium cepa chromosomes.In this karyotype, heterochromatin replicates late in the S period and there is a considerable amount of late replicating DNA that is not heterochromatic preferentially located in pericentromeric regions. In short, we discuss the detailed morphology and late replication pattern of the onion karyotype.