Question

when does crossing over occur?
prophase i
metaphase i
anaphase i
telophase i
prophase ii
metaphase ii
anaphase ii
telophase ii

Explanation:

Crossing over, which involves the exchange of genetic material between homologous chromosomes, occurs during prophase I of meiosis. This is when homologous chromosomes pair up (synapsis) and form structures called chiasmata where the exchange takes place. In metaphase I, chromosomes align at the equator; in anaphase I, homologous chromosomes separate; in telophase I, the first meiotic division nears completion. Prophase II, metaphase II, anaphase II, and telophase II are part of meiosis II where no crossing - over occurs as there are no homologous chromosome pairings (except in some rare cases of aberrant meiosis, but the standard case is no crossing - over).

Answer:

prophase I