If meiosis II products have 10 chromosomes and 20 picogram DNA, then what will be the number of chromosomes and DNA amount respectively in G2 phase of meiocyte?
(1) 20 and 40 Pg DNA (2) 40 and 80 Pg DNA
(3) 20 and 20 Pg DNA (4) 20 and 80 Pg DNA
And the answer is given (4). I cant understand the explanation given also:--
Answer (4) In normal meiocyte,, chromosome = 2n
DNA = 2C
G₁ = 2n, 2C
S = 2n, 4C
G₂ = 2n, 4C
After meiosis II,,n, 1C in each haploid cell

Hi Meemansha,
Please find below the solution to the asked query:

The correct option is (4).

Meiosis II products are the four haploid cells with half number of chromosomes as compared to normal cell and 1/4 of DNA content as compared to the cell at S phase or G₂ phase .
These four cells are haploid i.e their chromosome number = n (here n is given as 10 chromosomes)
The amount of the DNA in these cells is given as 1C = 20 picogram.

1. As we know normal meiocyte is a diploid cell, so its chromosome number is = 2n (n refers to haploid number of chromosomes) and its DNA amount is 2C (C refers to amount of DNA in picogram).
2. Now, when cell starts dividing, it first enters the G₁ phase of cell cycle. During this phase only growth of cell takes place and the chromosome number and DNA content remains same. Thus, meiocyte in this phase will have same 2n chromosome number and 2C DNA content.
3. Now, cell enters S phase of cell cycle. In this phase, the replication of parental DNA takes place, so the DNA content becomes double here i.e 4C. However, the parental DNA and newly synthesised DNA is still attached at centromere, so chromosome number remains same i.e 2n.. Hence in this phase chromosome number = 2n and DNA content = 4C.
4. After this phase, cell enters G₂ phase. Here cell again grows and does not replicate any DNA. Thus, here also chromosome number and DNA content remains unchanged i.e chromosome number = 2n and DNA content = 4C.
5. After G₂ phase, the cell under goes meiosis I that produces two daughter cells with chromosome number and DNA content reduced to half. Thus, each of the two new cells will have chromosome number = n = 10 chromosomes and DNA content = 2C= 40 picogram.
6. After this, these two cells undergo meiosis II to produce four haploid cells. In this division, the chromosome number remains same but each cell will have now 1/4 DNA content (because four cells are produced) as compared to the cells in G₂ phase i.e = 80/4 = 20 picogram. Thus, each of the four cells produced from meiocyte will have n = 10 chromosomes and only 20C i.e 20 picogram DNA after meiosis II.
7. In the question, it is given that n = 10 and C = 20 after meiosis II. Thus in G₂ phase, meiocyte will have chromosome number = 2(n) = 2(10) =20 chromosomes and DNA content = 4 (C) = 4(20) = 80 picogram.

Hope this information will clear your doubts about the number of chromosomes and amount of DNA in a meiocyte in G2 phase when meiosis II products have 10 chromosomes and 20 picogram DNA.
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