[The associations of acrocentric chromosomes in the parents of Down's syndrome children (a review of the literature)].

A point of view has been recently maintained that, as data are accumulated, the role of the association activity as a cause of acrocentric chromosome nondisjunction is not confirmed. Data are reviewed concerning all the studies available in the literature on the frequency and pattern of acrocentric associations in parents of the Down's syndrome patients. From these data it is evident that the nucleolar organizing activity is an important factor in etiology of trisomy 21. Reasons of some negative results occasionally reported are discussed.