Figure 1

Fluorescent signals in PHA-stimulated lymphocytes at interphase following FISH with the CEN17 probe. (A) Cell with two singlets (SS cell), in which neither allele has replicated; (B) cell with two doublets (DD cell), in which both alleles have replicated; and (C) cell with one singlet and one doublet (SD cell), a S-phase cell in which one allele has replicated while its partner has still to do so.