When a single diploid cell completes meiosis I and meiosis II, what is the final outcome in terms of the number and ploidy of daughter cells produced?

Introduction / Context:
Meiosis is a special type of cell division that produces gametes such as sperm and ova. It reduces the chromosome number by half so that fertilization can restore the diploid number. This question asks about the ultimate result when one diploid cell undergoes the full process of meiosis, including both meiosis I and meiosis II.

Given Data / Assumptions:

• We start with one diploid parent cell.
• The cell undergoes meiosis I followed by meiosis II.
• We must state the number and ploidy of the final daughter cells.

Concept / Approach:
In diploid organisms, somatic cells have two sets of chromosomes, one from each parent. Meiosis involves two successive divisions. Meiosis I is a reductional division where homologous chromosomes separate, reducing the chromosome number from diploid to haploid. Meiosis II is similar to mitosis, where sister chromatids separate, but the chromosome number remains haploid. After both divisions, each original diploid cell yields four genetically distinct haploid cells.

Step-by-Step Solution:
Step 1: Begin with one diploid cell, written as 2n. Step 2: During meiosis I, homologous chromosomes pair up and then separate into two daughter cells. Each daughter cell now has n chromosomes, so two haploid cells are formed. Step 3: Each of these haploid cells enters meiosis II, where the sister chromatids separate, producing two haploid cells from each original haploid cell. Step 4: In total, from one diploid cell, four haploid cells are produced by the end of meiosis II.

Verification / Alternative check:
Human gamete formation is a clear example. The diploid germ cell in the testes or ovaries has 46 chromosomes. After meiosis, each sperm or ovum contains 23 chromosomes, which is haploid. Since meiosis produces four gametes from one original cell, this matches the general rule that one diploid cell yields four haploid cells after completing meiosis I and II.

Why Other Options Are Wrong:

• Option A (Two haploid cells): This would be correct if meiosis stopped after meiosis I, but the question includes both meiotic divisions.
• Option C (Two diploid cells): This describes the typical outcome of mitosis, not meiosis.
• Option D (Four diploid cells): This also conflicts with the defining feature of meiosis, which is reduction of chromosome number.

Common Pitfalls:
Students sometimes confuse meiosis with mitosis, leading to incorrect answers about chromosome number and cell count. Another confusion arises from counting cells after only one division instead of both. It helps to remember that meiosis has two stages and that the final goal is to produce four haploid cells for sexual reproduction.

Final Answer:
When a diploid cell completes meiosis I and meiosis II, it produces four haploid cells.