Final answer:
When nondisjunction occurs during mitosis, one daughter cell will have an extra chromosome (2n + 1), and the other will have one fewer (2n - 1).
Step-by-step explanation:
During mitosis of a diploid cell, if nondisjunction occurs, it means that a pair of sister chromatids failed to separate properly. As a result, one of the resulting daughter cells will have an additional chromosome (making its chromosome number 2n + 1), while the other daughter cell will be missing a chromosome (making its chromosome number 2n - 1). In a normal diploid cell undergoing mitosis without any errors, each daughter cell is expected to have the same chromosome number as the parent cell (2n).