Heterochromatinization of human X-chromosomes: classification of replication profile.

The replication profiles of human X-chromosomes are studied by RBA-technique. It is suggested that the late replicating X-chromosome can be arbitrarily classified into 8 types. Furthermore, data suggest that the individual cells are under self-control pertaining to the inactivated X-chromosome. This may reflect that the altered chromatin may not be uniform in the process of inactivation.