B Predivision was predominant in biparental meiosis. Chromosome segregation error patterns were categorized based on anaphase trajectories: nondisjunction (0:4 segregation), balanced predivision (2:2 sister chromatid segregation), unbalanced predivision (1:3 segregation including sister chromatid segregation), and complex patterns including predivision (multiple errors including sister chromatid segregation). Chromosome breakages (chromosomes lacking centromeres) were also observed. Data from 39 and 17 oocytes, respectively. 