In PHA-cultured lymphocytes, about 8% of metaphases from 32 women were aneuploid compared to 4% of metaphases from 35 men. A significant part of this aneuploidy was characterized by sex chromosome involvement: in women, the loss of gain of X chromosomes; in men, the gain of X chromosomes and the loss or gain of Y chromosomes. The incidence of this aneuploidy was positively age-related for both sexes. Premature division of the X-chromosome centromere was closely associated with X-chromosome aneuploidy in women and men, and appeared to be the mechanism of non disjunction causing this aneuploidy. Premature centromere division (PCD) indicated a dysfunction of the X-chromosome centromere with aging, and this dysfunction was the basic cause of age-related aneuploidy. A similar mechanism of nondisjunction may operate for the Y chromosome of men, but could not be clearly demonstrated because of the low incidence of Y-chromosome aneuploidy. The balance of the aneuploidy was characterized by chromosome loss and the involvement of all chromosome groups. It was consistent with chromosome loss from metaphase cells damaged during preparation for cytogenetic examination.
About 20% of leukemic bone marrow cells from each of two patients with B-cell lymphoid leukemias showed apparent translocations which appeared to be the result of telomeric association. In one patient, whole chromosomes were associated telomere to telomere in pairs; in the other patient, telomeres of whole chromosomes were associated with breakpoints located close to the proximal or distal ends of the heterochromatic band 1q12. Repeated base sequences, particularly (CA)n sequences, are believed to be the basis of telomere pairing, and likewise repeated base sequences of heterochromatin may explain the association of 1qh and telomeres. Telomeric association may be considered as a potential origin of new stable cytogenetic combinations that have a role in oncogene transposition and tumor etiology.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.