Question

If the dna content of a diploid cell in the g1 phase of the cell cycle is represented by x, then the dna content of the same cell at metaphase of meiosis i would be 2x. if we continued to follow the cell lineage, the dna content of a cell at metaphase of meiosis ii would be

Answer 1

Mitosis and meiosis are both cell division process except that the former is only done by somatic cells and the latter is done by gametes. In G1 phase or the growth phase of interphase, there is increase in cellular substance without DNA replication therefore DNA will be regarded as x. By the time when S or synthesis phase of interphase is finished, DNA replication is done therefore all phases that follow the S phase will have a DNA of 2x. In this case, the cell in metaphase of meiosis I has double the amount of DNA than the one in G1 phase because this cell already underwent the S phase. In meiosis, after the first division (meiosis I), there is reduction of genetic material into half (hence called reduction division) producing haploid cells. So a cell in the metaphase of meiosis II will have DNA half of that in metaphase of meiosis I thereby regarded as x.

Answer 2

x DNA content in the G1 phase of a cell in the cell cycle is 2n. So 2n = x (given) Similarly the DNA content of the same cell in the cell cycle is 4n. This is equal to 2x (given). In the same way continuing with the lineage that is in the cell cycle, the DNA content will be 2n, which is again x.