Position of late and early replicating human X chromosomes at somatic metaphase.

The location of late and early replicating human X chromosomes was determined in metaphases obtained from human females using the RBA technique. The late replicating X chromosome was not observed preferentially in a peripheral location. Nevertheless, a consistent pattern was observed in the location of both sex chromosomes from the pooled observations. The distance between the two X chromosomes did not vary significantly (P greater than 0.05) from person to person. The earlier hypothesis that late replicating autosomes containing genetically less active chromatin are accumulated at the periphery of the nucleus in plant cells was not observed in human somatic cells.