Question

Choose the correct statements:
A. During mitosis each nucleus divides only once after every synthesis phase
B. There is no DNA synthesis during mitosis while 0.3% of DNA is synthesized during meiosis
C. After anaphase chromosome no is '2 n' in mitosis and 'n' after second anaphase of meiosis
D. Generally crossing over takes place in mitosis and not in meiosis
E. Crossing over takes place in meiosis

• A. A, B, C, D, E only
• B. A, B, E only
• C. B, C, E only
• D. A, B, C, E only

Hint:

Crossing over during meiosis creates genetic variability, which is essential for evolution and adaptation.

Answer 1

The Correct Option is D

Concept: Mitosis and meiosis are two major forms of cell division. Mitosis maintains chromosome number, whereas meiosis reduces chromosome number and introduces genetic variation.

Step 1: Analyze statements A and B.
In mitosis, each nucleus divides only once after DNA synthesis during interphase. During meiosis, a very small amount of DNA synthesis may occur during prophase-I for recombination and repair processes. Thus, statements A and B are correct.

Step 2: Analyze statements C, D, and E.
After mitotic anaphase, daughter nuclei remain diploid (2n). After meiosis-II, chromosome number becomes haploid (n). Crossing over is a characteristic feature of meiosis, especially during pachytene of prophase-I, and generally does not occur during mitosis. Hence, statements A, B, C, and E are correct.