Two individuals have the following genotypes: X K X r and X r Y . Part 1 The couple has a child that is X R X r X r . Then the nondisjunction event occurred in the mother. the father. could be either. Part 2 The nondisjunction occurred in the mother, and their child is X R X R Y . Given this genotype, the nondisjunction most likely occurred in: meiosis I. meiosis II. could be either..