Aneuploidy induced by agricultural pesticides: where do we stand?

Even though aneuploidy is one of the worst afflictions of man, efforts to develop a mammalian test system for the study of induced nondisjunction have largely failed. A few scattered successes usually deal with Drosophila, fungi, plants, and mammalian cell cultures. The present paper discusses possible avenues to be explored for developing reliable test systems. These include: (i) epidemiological studies, (ii) analysis of fluorescent Y bodies, (iii) direct visualization of sperm chromosomes, (iv) analysis of out-of-phase centromere separation sequences, and (v) the soybean spot test. Currently there is no satisfactory explanation for a lack of mutagen-induced nondisjunction, the repeated occurrence of births of trisomic children to some couples, the astounding success of selection of a rare disomic sperm for fertilizing an egg in the presence of millions of normal ones, and having twice as many errors occurring in meiosis I as in meiosis II. An hypothesis is presented which suggests that out-of-phase separation of a centromere during early embryogenesis results in formation of mosaic individuals. Such mosaicism for a given chromosome in the gametic tissue would account for all the dilemmas mentioned above. Some supporting evidence for this concept is presented. It requires a new look at the mechanism of the origin and potential of transmission of aneusomic gametes.