Which best describes meiosis, and how does it differ from mitosis in terms of genetic diversity and ...

Meiosis is a specialized type of cell division that reduces the chromosome number by half, resulting in the production of four genetically distinct haploid cells. This process is essential for sexual reproduction and contributes to genetic diversity. Meiosis consists of two consecutive divisions, meiosis I and meiosis II, each with its own phases: prophase, metaphase, anaphase, and telophase.

Here is a step-by-step description of meiosis:

Meiosis I:

1. Prophase I: Chromosomes condense and homologous chromosomes pair up in a process called synapsis. Crossing over occurs, where segments of DNA are exchanged between non-sister chromatids of homologous chromosomes, leading to genetic recombination.

2. Metaphase I: Paired homologous chromosomes (tetrads) align at the metaphase plate. The orientation of each pair is random, contributing to genetic variation through independent assortment.

3. Anaphase I: Homologous chromosomes are pulled apart by spindle fibers and move to opposite poles of the cell. Unlike mitosis, sister chromatids remain together.

4. Telophase I and Cytokinesis: Chromosomes arrive at the poles, and the cell divides into two haploid cells. Each cell has half the number of chromosomes, each consisting of two sister chromatids.

Meiosis II:

1. Prophase II: Chromosomes condense again, and a new spindle apparatus forms in each of the two haploid cells.

2. Metaphase II: Chromosomes line up individually along the metaphase plate in each cell.

3. Anaphase II: Sister chromatids are finally separated and move to opposite poles of the cell.

4. Telophase II and Cytokinesis: Chromatids reach the poles, nuclear membranes reform, and the cells divide, resulting in four genetically unique haploid cells.

Comparison with Mitosis:

Mitosis is a process of cell division that results in two genetically identical diploid daughter cells. It is used for growth, repair, and asexual reproduction in eukaryotic organisms. Here are the key differences between meiosis and mitosis:

- Genetic Diversity: Meiosis increases genetic diversity through crossing over during prophase I and independent assortment during metaphase I. Mitosis does not contribute to genetic diversity as it produces identical daughter cells.

- Cell Function: Meiosis produces gametes (sperm and eggs) for sexual reproduction, each with half the number of chromosomes of the parent cell. Mitosis produces cells for growth, repair, and asexual reproduction, maintaining the same chromosome number as the parent cell.

- Number of Divisions: Meiosis involves two rounds of division (meiosis I and II), while mitosis involves only one.

- Number of Daughter Cells: Meiosis results in four haploid daughter cells, whereas mitosis results in two diploid daughter cells.

- Chromosome Number: Meiosis reduces the chromosome number by half, creating haploid cells. Mitosis maintains the original chromosome number, producing diploid cells.

In summary, meiosis is a two-step division process that generates genetic diversity and is essential for sexual reproduction, while mitosis is a single division process that maintains genetic consistency and is used for growth and repair.