Explain how to determine if a nondisjunction occurred during meiosis I or meiosis II and what the ...

If nondisjunction occurs in meiosis I, all gametes will be abnormal and carry either both members of a chromosomal pair or neither member of the pair. Nondisjunction in meiosis II produces 50 normal haploid cells and 50 abnormal cells, one with an extra copy of a chromosome and one missing a chromosome. Fertilization between gametes with an extra copy of a chromosome and a haploid gamete will result in trisomy; fusion of a haploid gamete and one missing a copy of a specific chromosome will result in monosomy. The phenotypic effects of aneuploidy range from minor physical symptoms to devastating and lethal conditions. Among survivors, phenotypic effects often include behavioral deficits and intellectual disability.