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.