The origin of human triploids

Abstract

A series of 26 triploid foetuses was ascertained in a survey of spontaneous abortuses and the origin of the additional haploid complement determined in 21 of them by the study of foetal and parental heteromorphisms. In 17 the additional haploid set was paternal in origin, in 3 it was maternal in origin and in one the parental origin could not be determined. The best fit for the data using a maximum-likelihood method was that 66.4% of the triploids were the result of dispermy, 23.6% the result of fertilization of a haploid ovum by a diploid sperm formed by failure of the first meiotic division in the male and 10% the result of a diploid egg formed by failure of the first maternal meiotic division. The possible sources of error inherent in the technique are reviewed and our results compared with previously published data.

Mammalian membrane block to polyspermy: new insights into how mammalian eggs prevent fertilisation by multiple sperm

“…Polyploidy will generally be fatal to an embryo and has been detected in approximately 10-20% of spontaneously aborted human conceptuses (Jacobs et al 1978;Hassold et al 1980;Michelmann et al 1986). Polyploid embryos can result from either digyny (due to errors in meiosis I during oocyte maturation or meiosis II during egg activation) or diandry (due to fertilisation by a diploid sperm or by two sperm).…”

“…Polyploid embryos can result from either digyny (due to errors in meiosis I during oocyte maturation or meiosis II during egg activation) or diandry (due to fertilisation by a diploid sperm or by two sperm). The majority of triploid human embryos appear to be the result of polyspermic fertilisation, with two sperm fertilising an egg (Jacobs et al 1978;Zaragoza et al 2000). Mammals use several mechanisms to prevent polyspermy (addressed below), although, even with these in place, the incidence of polyspermy is 1-2% when mating occurs around the time of ovulation.…”

“…Although most triploid embryos die early in embryogenesis, it is possible for some to survive into post-implantation development; studies of human embryos have found that a subset of triploid embryos survived well into gestation (average approximately 111 days in one study of 1000 abortions; Hassold et al 1980). A small number of triploid embryos has survived into the third trimester or to full term, but died shortly after birth (Jacobs et al 1978;Hassold et al 1980). It is thought that survival rates depend on the extent of mosaicism or what proportion of cells are diploid (Michelmann et al 1986).…”

Parental origin and mechanisms of formation of triploidy: a study of 25 cases

“…Early studies, based on the analysis of cytogenetic polymorphisms, suggested a clear predominance of diandric cases. [7][8][9] More recent studies, based on the molecular analysis of microsatellite markers, clearly indicate that triploidies of maternal origin are far more frequent than those of paternal origin in foetuses with gestational ages of 10 weeks or more. 5,10 Reasons for the discrepancies could be first of all related to the different methods used for ascertaining the parental origin of the triploidies; indeed, the use of molecular markers as opposed to cytogenetic polymorphisms allows a higher degree of accuracy.…”

Chromosomal analysis of embryos produced by artificially inseminated superovulated cattle

“…In humans, chromosomal abnormalities in the embryo or fetus are the most frequent causes of malformations and pregnancy failure (Jacobs et al, 1978). Chromosomal analysis of cattle embryos at the morula and blastocyst stages, when embryo transfer is usually performed, has revealed abnormalities that are thought to compromise development (King, 1991).…”