Crossover occurs at the end of prophase I of meiosis. In the process of meiosis, homologous chromosomes, before dispersing into different nuclei, line up against each other, conjugate (connect), intersect, exchange sites. Crossover can occur on any chromosome. The genes that are part of the linkage groups in the chromosomes of the parental individuals, as a result of crossing-over, are separated, form new combinations and in this new form fall into gametes. Crossover is an important source of the emergence of new combinations of genes in the genotypes of individuals and the occurrence of variation of characters. It plays an important role in evolution, as it contributes to the emergence of hereditary variability.
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