Final answer:
Double stranded breaks begin in Zygotene and recombination is complete by Pachytene. The correct answer is b) Zygotene, pachytene.
Step-by-step explanation:
During meiosis, the process of genetic recombination occurs in the prophase I stage. In Zygotene, the homologous chromosomes start to pair up and form structures called synaptonemal complexes. This is when the double stranded breaks, also known as DNA cleavage, begin to happen. As prophase I progresses, the chromosomes continue to condense and the recombination process is completed by Pachytene.
At the end of prophase I, the chromosomes are held together at points called chiasmata. The chiasmata are resolved by late pachytene, marking the completion of recombination. In conclusion, double stranded breaks begin in Zygotene and recombination is complete by Pachytene during meiosis. The correct answer is b) Zygotene, pachytene