Final answer:
Nondisjunction during meiosis I results in all abnormal gametes, while nondisjunction during meiosis II results in two normal and two abnormal gametes. The statement that 50% of the gametes will be normal is incorrect for both meiosis I and II.
Step-by-step explanation:
When uneven crossing over occurs during meiosis, the four resulting gametes will not be genetically identical. Depending on when the nondisjunction occurs, different outcomes can be observed:
- If homologous chromosomes fail to separate during meiosis I, all four gametes will be abnormal, with two gametes lacking that chromosome and two gametes having two copies of it.
- If sister chromatids fail to separate during meiosis II, there will be two normal gametes with one copy of each chromosome, one gamete with two copies, and one gamete with no copies of the faulty chromosome.
Therefore, answers b and c are incorrect since nondisjunction in meiosis I or II does not result in 50% normal gametes. The correct answer is a: nondisjunction results in gametes with n+1 or n-1 chromosomes, not four different kinds of gametes as suggested by answer d.