How many cells are produced by the end of Meiosis II?
The correct answer and explanation is :
At the end of Meiosis II, four haploid cells are produced.
Explanation:
Meiosis is the type of cell division responsible for creating gametes (sperm and egg cells in humans) and reducing the chromosome number by half, ensuring that when gametes fuse during fertilization, the resulting zygote has a complete set of chromosomes. Meiosis consists of two stages: Meiosis I and Meiosis II.
Meiosis I:
- During Meiosis I, homologous chromosomes are separated into two different cells. This phase involves:
- Prophase I: Chromosomes condense, homologous chromosomes pair up (synapsis), and crossing-over occurs.
- Metaphase I: Homologous chromosome pairs align along the metaphase plate.
- Anaphase I: Homologous chromosomes are pulled to opposite poles (but sister chromatids remain attached).
- Telophase I and Cytokinesis: The cell divides into two daughter cells, each with half the chromosome number (haploid).
Meiosis II:
- Meiosis II follows the same basic steps as mitosis but without the DNA replication step.
- It’s essentially a division of sister chromatids rather than homologous chromosomes.
- Prophase II: Chromosomes (with two sister chromatids) condense, and a new spindle apparatus forms in each of the two haploid cells from Meiosis I.
- Metaphase II: Chromosomes align along the metaphase plate in both haploid cells.
- Anaphase II: The sister chromatids of each chromosome are separated and pulled toward opposite poles.
- Telophase II and Cytokinesis: The cells divide again, resulting in a total of four haploid cells, each with half the original chromosome number.
Conclusion:
- Meiosis reduces the chromosome number by half, and after two divisions (Meiosis I and Meiosis II), four non-identical haploid cells are produced. Each of these cells is genetically unique due to processes like crossing over in Meiosis I and independent assortment.