Question

Dna content in a meiocyte at g2 phase is 40 pg. What would be the dna content after meiosis-ii in the daughter cells ? (1) 20 pg (2) 5 pg (3) 10 pg (4) 15 pg

Answer 1

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.

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).

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.

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.

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.

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.

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.

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.

Answer 2

Option1. The DNA content after meiosis II in the daughter cells is 20 pg.

• G2 Phase or growth phase is known as the preparatory phase during which there is no division of the cell.
• Hence the DNA content is the same as the original parent cell.
• At the G2 Phase the DNA content is 40 pg.
• At the end of meiosis II, 4 daughter cells are formed. Each contains half the DNA content from the original parent cell.
• Therefore the DNA content after meiosis II will be 20 pg. in each cell.