Why is it important that chromosomes can cross over in Meiosis and not in Mitosis? Solution Crossing over results in genetic recombination. It is responsible for genetic diversity of the population. Genetic recombination and natural selection are the driving force behind evolution. Meiosis is called sex division, it is responsible for gamate formation. Crossing over occurs when chiasma is formed and this random exchange of information leads to unique gametes formation and genetic recombination to occur..