What is a major difference between meiosis II and mitosis in a diploid animal?

• A. DNA replication occurs before both meiosis II and mitosis.
• B. Meiosis II results in the formation of four daughter cells, while mitosis produces two.
• C. Homologous chromosomes separate during meiosis II, but not during mitosis.
• D. Meiosis II occurs in haploid cells, while mitosis occurs in diploid cells.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the context of the question. Meiosis and mitosis are two different types of cell division. Mitosis occurs in somatic (body) cells and results in two genetically identical diploid daughter cells. Meiosis, on the other hand, occurs in germ cells and results in the production of gametes (sperm or egg cells) through two rounds of division: meiosis I and meiosis II.
2. Step 2: Recall the key difference between meiosis II and mitosis. Meiosis II is the second division in meiosis and occurs in haploid cells (cells with one set of chromosomes), while mitosis occurs in diploid cells (cells with two sets of chromosomes). This is because meiosis I reduces the chromosome number by half, creating haploid cells, whereas mitosis maintains the diploid state.
3. Step 3: Analyze the options provided in the question. Option 1 states that DNA replication occurs before both meiosis II and mitosis, which is incorrect because DNA replication occurs only once before meiosis I, not before meiosis II. Option 2 states that meiosis II results in four daughter cells, while mitosis produces two, which is misleading because the four cells are the result of the entire meiosis process, not just meiosis II. Option 3 states that homologous chromosomes separate during meiosis II, but this is incorrect because homologous chromosomes separate during meiosis I, not meiosis II.
4. Step 4: Focus on the correct answer. The correct answer is that meiosis II occurs in haploid cells, while mitosis occurs in diploid cells. This distinction is crucial because it highlights the fundamental difference in the starting chromosome number of the cells undergoing these processes.
5. Step 5: Summarize the reasoning. Meiosis II and mitosis are similar in that sister chromatids separate in both processes. However, the key difference lies in the ploidy of the starting cells: meiosis II starts with haploid cells (due to the reduction in chromosome number during meiosis I), while mitosis starts with diploid cells. This difference is essential for understanding how meiosis contributes to genetic diversity and gamete formation.