LAUSR

Ovarian mature cystic teratomas (MCTs) originate from post‐meiotic germ cells. Conventional methods such as karyotyping or short tandem repeat‐polymorphism analysis may be used to better classify MCTs, although such data would be insufficient. The aim of this study was to elucidate the origin of ovarian MCTs using B allele‐frequency (BAF) plots of single nucleotide polymorphism array data. MCTs can be classified in terms of the zygosity of the centromeres and distal chromosome regions. We evaluated the zygosity of all chromosomes from 38 MCT specimens using BAF plot data. BAF plots were used to determine the homozygous and heterozygous regions over the whole genome. Theoretically, MCTs originated from the fusion of two ova (previously referred to as type V MCTs) should have a mixed pattern of centromeric zygosity, that is, a combination of heterozygous and homozygous regions in the centromeric regions. However, no MCTs in this study met this criterion. We identified 13 type I MCTs, 14 type II MCTs, and 11 type III MCTs. In addition, BAF plots facilitated the construction of recombination maps at the whole‐genome level for type I and II MCTs. No crossover, especially in the short arms, contributed to the failure of meiosis I, resulting in type I MCTs. Crossover in all arms might assure the normal progress of meiosis in human oocytes. In conclusion, our findings indicate that BAF plots can elucidate the developmental mechanism of MCTs, and further serve as useful analytical tools for analyzing human oocyte meiosis, and related aberrations.