Question: when does crossing over occur in prophase 1
[{'answer': 'pachytene stage', 'provenance': [{'wikipedia_id': '64045', 'title': 'Chromosomal crossover', 'start_paragraph_id': 21, 'start_character': 457, 'end_paragraph_id': 21, 'end_character': 472, 'bleu_score': 1.0, 'section': 'Section::::Chemistry.:Chiasma.\n'}]}, {'provenance': [{'wikipedia_id': '64045', 'title': 'Chromosomal crossover', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 586, 'bleu_score': 0.9205847666823811, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2973604391865010165}, 'section': 'Section::::Abstract.'}]}]