Question

If you have 200 ng of DNA in the G2 phase of the cell cycle, how much DNA will you have in prophase of mitosis? in prophase I if meiosis? in prophase II of meiosis? in telophase II of meiosis?

How many strands (molecules) of DNA are there per chromosome in prophase of mitosis? in prophase I if meiosis? in prophase II of meiosis? in telophase II of meiosis?

Answer 1

Answer-

1. In G2 phase 200ng of DNA is present which is duplicated in S phase of cell cycle. This means that before S phase DNA would be 100ng (2n) and after S phase DNA would be 200ng (4n).

2. When cell enters mitosis, in prophase 200ng of DNA is present as cell is 4n and cell is not divided yet. The 4n cell when enters in meiosis, in prophase l 200ng of DNA is present because cell is not divided yet. But in prophase ll cell is divided by meiosis l so that DNA content will be 100ng. And in telophase ll cell is again divided be meiosis ll so that haploid cell with 50ng of DNA would be present at this phase.

3. In prophase of mitosis, 4 DNA molecules per chromosome is present because in this phase cell is 4n.

4. In prophase l of meiosis, 4 DNA molecules per chromosome is present because at this phase cell is 4n and 200ng will be concentration of DNA.  

5. In prophase ll of meiosis, 2 DNA molecules per chromosome is present because at this phase cell is 2n and 100ng will be concentration of DNA.

6. In telophase ll of meiosis, only 1DNA per chromosome is present because at this phase cell is haploid and 50 mg will be concentration of DNA.