When homologous chromosomes line up during meiosis and one arm of a chromatid crosses over the arm of another chromatid, this process is known as crossing over or recombination. The result of this event is:
additional variation in the DNA combination of each sex cell formed.
Crossing over allows for the exchange of genetic material between homologous chromosomes, leading to new combinations of alleles in the resulting gametes. This increased genetic diversity is a key feature of sexual reproduction.