Question

Let 10X be the amount of DNA present in the gamete of an organism. How much DNA (for example: X, 2X, 5X, 20X, etc) would you expect to find in each of the following situations and briefly explain why:

a) a cell during metaphase I of meiosis

b) a cell in G2

c) a daughter cell following mitosis

d) a nucleus in mitotic prophase

e) a cell in G0 f) a cell resulting from meiosis II

Answer 1

A gamete is a Haploid (N) cell which after fusion with another gamete during fertilization forms a diploid organism (2N).

Amount of DNA in gamete = 10X

Amount of DNA in the cell will be = 20X

Amount of DNA :-

(a) a cell during metaphase I of meiosis - 40X

(b) a cell in G2 phase - 40X

(c) a daughter cell following mitosis - 20X

(d) a nucleus in mitotic prophase - 40X

(e) a cell in G0 phase - 20X

(f) a cell resulting from meiosis II - 10X

?A cell having DNA content 20X at G1 and G0 phase as the ploidy level will be 2N.

?In S phase there will be DNA synthesis so the DNA amount will be doubled 40X without change in Chromosome number.

?In G2 phase and prophase of mitosis it will remain same as of S phase i.e. 40X.

? Completion of mitosis the amount of DNA will be 20X.

?In meiosis, the cell during metaphase I will have 40X of DNA as of S and G2 phase. This DNA amount will be halved after Telomerase I.

?After completion of meiosis II, the DNA content in the daughter cell will be 10X, halved the amount in the parent cell.