Parental origin of triploidy and trisomy in human miscarriages

Abstract

Caspersson (1970) discovered that each chromosome pair has a characteristic banding pattern when chromosomes are stained with the fluorescent dye, quinacrine. With this dye there are certain chromosome regions which are polymorphic. These regions can be used as markers in the study of the inheritance of chromosome anomalies. The purpose of this study was to determine, using chromosome markers, the parental origin of the extra chromosomes found in triploid and D, G trisomic spontaneous abortuses. Polymorphisms in the chromosomes of parents of 15 triploid and 12 trisomic abortuses were compared with those of their abortus to determine which parent donated the extra chromosome(s). The distribution of the markers was used to determine whether the error occurred during meiosis I or meiosis II or, in the case of triploids, to distinguish between a meiotic error and dispermy. Of the 15 triploids examined, 7 were informative as to the origin of the extra set of chromosomes. In 3 of these there was failure to extrude to second polar body during oogenesis. In 3 other cases it was impossible to distinguish between an error during meiosis of spermatogenesis and dispermy. The other informative case definitely arose by dispermy. Mechanisms for the origin of triploidy were discussed, in particular, aging of gametes. Only 1 of the 12 trisomies examined was informative. This was a trisomy 22 in which the extra 22 was from the mother but it was not possible to distinguish between non-disjunction during meiosis I and meiosis II. Possible mechanisms for the production of trisomies were discussed including maternal irradiation, autoimmune processes, possible endocrine factors and drugs.</p> <p>A number of technical factors which influence the appearance of polymorphic regions were also discussed.