Question

what is crossing over? in which cell division it takes place? what is its significance?

Answer 1

Crossing over is the exchange of genes between two chromosomes, resulting in non-identical chromatids that comprise the genetic material of gametes. This process occurs during Prophase I of Meiosis, just prior to chromosome alignment and splitting of the cell.
this may help you.

Answer 2

In meiosis cell division the crossing over takes place. the crossing over is gene exchange.