Question

Look at the figure given below. The number given inside the circle represents the number of chromosomes in the cell at that point. Fill in the blanks for (i), (ii) and (iii) using the option that fits best.

• A. (i) - 40; (ii) - 20; (iii) - 10
• B. (i) - 40; (ii) - 10; (iii) - 10
• C. (i) - 20; (ii) - 10; (iii) - 10
• D. (i) - 40; (ii) - 20; (iii) - 20

Answer 1

The correct option is D (i) - 40; (ii) - 20; (iii) - 20

Meiosis is a type of cell division that occurs in sexually reproducing organisms which reduces the chromosome number by half, resulting in the formation of haploid daughter cells. Meiosis involves a single cycle of DNA replication followed by two cycles of nuclear division and cell division.

Meiosis I: It is a reduction division. The two daughter cells formed at the end of meiosis I are haploid and have only half the number of chromosomes as the parent cell. In the question, since at the end of meiosis I, the haploid daughter cells have 20 chromosomes each, the diploid parent cell must have had 40 chromosomes.

Meiosis II: It is an equational division and hence, the chromosome number of the parent cells and the daughter cells remain the same. Thus, the four daughter cells formed after meiosis II will have 20 chromosomes each, just like the haploid parent cells.