Aneuploidy
 
 An aneuploid cell has one or more complete chromosomes either in excess or less than the normal haploid, diploid, or polyploid number characteristic of the species from which the cell derives. In other words, the chromosome number is not a multiple of the haploid cell number of chromosome.
Fluorescence in situ hybridization (FISH) with chromosome-specific probes has been successfully applied to rapidly detect numerical aberrations in metaphase and interphase amniotic cells (1.( Aneuploidy arises primarily by the process of nondisjunction, probably caused by nonrandom premature centromere division in the first meiotic division of maternal meiosis. This varies among chromosomes, however, and a significant proportion of paternal and/or meiosis II errors have been described.
 The presence of kinetochores or kinetochore proteins (detected immunochemically) in the micronuclei of binucleated cells indicates a cell with a high probability for aneuploidy following cytokinesis (2, 3). The relationship between Y-Chromosome aneuploidy in male humans, the number of micronuclei, the status of kinetochore proteins, and aging has been reviewed (4).
References
1. W. L. Kuo et al. (1991) Am. J. Hum. Genet. 49, 112–119. 
2. D. A. Eastmond and J. D. Tucker (1989) Mutat. Res. 224, 517–525. 
3. B. K. Vig, H. J. Yoo, and D. Schiffmann (1991) Mutagenesis 5, 361–367. 
4. J. Nath, J. D. Tucker, and J. C. Hando (1995) Chromosoma 103, 725–731.