When homologous chromosomes crossover, what occurs? - Maternal alleles are "corrected" to be like paternal alleles and vice versa. - Two sister chromatids exchange identical pieces of DNA. - Each of the four DNA strands of a tetrad is broken and the pieces are mixed. - Specific proteins break the two strands and re-join them with their homologs. - Two chromatids get tangled, resulting in one re-sequencing its DNA.