Heterodisomy (Heterozygous) indicates a meiosis I error, whereas isodisomy (homozygous) indicates either a meiosis II error or postzygotic duplication.
Whereas isodisomy (homozygous) indicates either a meiosis II error or postzygotic duplication. This is what Heterodisomy (Heterozygous) indicates a meiosis I error.