Maternal Age Dependence of Chromosome Anomalies

Abstract

A NUMBER of hypotheses have been proposed to account for the well established fact that non-disjunction of chromosomes increases with advancing maternal age. Most are based on the assumption of mutational or cytoplasmic ageing in the prolonged dictyotene stage of the oocyte. Evans¹ suggested that virus or other infections cause the nucleolus to persist in the oocyte, preventing the separation of half-bivalents at anaphase-I. Edwards² found no evidence of nucleolar persistence in human oocytes, although he did not study this phenomenon in older animals.