Final answer:
A crossover between two loci restores the original allele arrangement by exchanging DNA segments between non-sister chromatids of homologous chromosomes, mixing maternal and paternal genes.
Step-by-step explanation:
If a crossover occurs between two loci, the original arrangement of alleles on each non-sister homolog is recovered. During crossing-over, segments of DNA are exchanged between non-sister chromatids of homologous chromosomes. This results in an exchange of genetic material between the chromosomes, leading to a mix of maternal and paternal genes in the recombinant chromatids that differs from the combination that existed before the crossover. It is important to distinguish this from a translocation, which refers to the exchange of segments between nonhomologous chromosomes and can result in changes to gene position relative to regulatory sequences.