The somatic cells of Drosophila contain 8 chromosomes. What is the number of chromosomes and DNA molecules in the nucleus during gametogenesis before the onset of meiosis I and meiosis II? Explain how so many chromosomes and DNA molecules form.
1) before the onset of meiosis I, the number of chromosomes is 8, the number of DNA molecules is 16;
2) before the start of meiosis I, the DNA is replicated, and each chromosome consists of two chromatids, but the number of chromosomes does not change;
3) before the start of meiosis II, the number of chromosomes is 4, the number of DNA molecules is 8;
4) before the start of meiosis II after the reduction division of meiosis I, the number of chromosomes and the number of DNA molecules decreases by 2 times.
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