Hello. You have not shown the model of meiosis to which the question refers, which makes it impossible for this question to be answered accurately. However, I will try to help you in the best possible way.
Crossing over is a genetic phenomenon that occurs when two sister chromatids are broken at some points and the pieces are exchanged between them. these exchanges cause the appearance of completely new gene sequences, which can completely affect the expression of stretches in the cells where the crossing over happened, since this cell will have a different gene sequence than the others.
As you may already know, chromosomes are formed by two filaments, called a chromatid. These filaments are united by the centromeros and the union of two filaments and a centromero is called sister chromatides.