Correct Response: A. Crossing over is the exchange of genetic material between homologous chromosomes. During prophase I of meiosis, synapsis occurs in which homologous chromosomes come together to form pairs, overlapping at several places along their lengths. At this time genetic material can be exchanged between the homologous chromosomes. Although homologous chromosomes are still paired during metaphase I (C), crossing over occurs most frequently during prophase I. Since homologous chromosomes have been separated into different daughter cells at the end of meiosis I, crossing over cannot occur during either prophase II (B) or metaphase II (D).
