Why does meiosis consist of two consecutive cell divisions (meiosis I and meiosis II)?

• A. To double the genetic material before fertilization occurs.
• B. To produce four identical daughter cells for tissue growth.
• C. To allow the cell to repair DNA damage before entering mitosis.
• D. To reduce the chromosome number by half and then separate sister chromatids, ensuring genetic diversity and the formation of haploid gametes.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the purpose of meiosis. Meiosis is a specialized type of cell division that occurs in sexually reproducing organisms to produce haploid gametes (sperm and egg cells). This ensures that the chromosome number is halved, maintaining the species' chromosome count after fertilization.
2. Step 2: Analyze the two stages of meiosis. Meiosis consists of two consecutive divisions: meiosis I and meiosis II. Each stage has distinct roles in reducing chromosome number and ensuring genetic diversity.
3. Step 3: Explain meiosis I. In meiosis I, homologous chromosomes (pairs of chromosomes, one from each parent) are separated. This reduces the chromosome number by half, transitioning the cell from diploid (2n) to haploid (n). Genetic recombination also occurs during crossing over in prophase I, increasing genetic diversity.
4. Step 4: Explain meiosis II. In meiosis II, the sister chromatids of each chromosome are separated. This division is similar to mitosis but occurs in haploid cells, ensuring that each gamete receives a single copy of each chromosome.
5. Step 5: Summarize the outcome. The two consecutive divisions of meiosis result in four haploid gametes, each genetically unique due to crossing over and independent assortment. This process is essential for sexual reproduction and genetic diversity in offspring.