The total mass of all DNA molecules in the 46 chromosomes of one human somatic cell is about 6 · 10 ^ −9 mg. Determine the mass of all DNA molecules in the cell nucleus during spermatogenesis before the onset of meiosis and after the end of meiosis. Explain the results.
1) before the onset of meiosis, the total mass of DNA molecules is: 2 · 6 · 10 ^ – 9 = 12 · 10 ^ – 9 mg; after meiosis, the DNA mass is: 12 · 10 ^ – 9: 4 = 3 · 10 ^ – 9 mg;
2) before the start of division, the number of DNA doubles, and the mass increases by 2 times;
3) after the end of meiosis, 4 haploid cells are formed, so the DNA mass decreases
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