Answer the following question given this paragraph: 

During crossing-over, segments of DNA are exchanged between non-sister chromatids of homologous chromosomes. Notice how this can result in an allele (A) on one chromosome being moved to the other chromosome. The four chromatids compose the tetrad, with a chiasma at the point of exchange.


Q: When does exchange of dna segments happen between non-sister chromatids of homologous chromosomes?


A:
during crossing-over