Crossing over is a universal phenomenon, observed in all groups of organisms from viruses to man. Its study is of great significance because of the following reasons:
1. Crossing over affords a proof for the linear arrangement of genes.
2. Crossing over has led to the construction of linkage maps or genetic maps of chromosomes, which are condensed graphic representation of the relative distances among the genes in a linkage group expressed in terms of percentage of recombination. Linkage maps of Drosophila and maize chromosomes have been constructed in details.
3. As a result of crossing over, new gene combination are produced which change the frequency of genes in genetic pool of a population.