Meiosis I nondisjunction

Homologous chromosomes fail to disjoin in meiosis I, and all resulting gametes are aneuploid. Fertilization by a normal haploid gamete produces fertilized eggs that are trisomic (2n + 1) or monosomic (2n  1)Homologous chromosomes fail to disjoin in meiosis I, and all resulting gametes are aneuploid. Fertilization by a normal haploid gamete produces fertilized eggs that are trisomic (2n + 1) or monosomic (2n  1)

Meiosis I Meiosis ll Secondary Fertilization (with Fertilized gametocytes Gametes anormal gamete) eggs Trisomic (2n + 1) (2n) Primary gametocyte (n) Monosomic (2n — 1) (n—1) (n—1)