 The diploid nature of chromosomes allows for genes on different chromosomes to assort independently or be separated from their homologous pair during sexual reproduction wherein haploid gametes are formed . In this way new combinations of genes can occur in the offspring of a mating pair . Genes on the same chromosome would theoretically never recombine . However , they do via the cellular process of chromosomal crossover . During crossover , chromosomes exchange stretches of DNA , effectively shuffling the gene alleles between the chromosomes . This process of chromosomal crossover generally occurs during meiosis , a series of cell divisions that creates haploid cells . 
