Mitosis: Cell Division and Growth

• Mitosis and meiosis are essential processes in cell division, vital for growth, repair, and reproduction in organisms
• Mitosis results in two identical daughter cells, while meiosis produces four genetically different daughter cells with half the number of chromosomes as the parent cell

Mitosis

• Mitosis results in daughter cells with the same number and kind of chromosomes as the parent nucleus
• It is typical of ordinary tissue growth
• It is a process of nuclear division in eukaryotic cells that produces two identical daughter cells from a parent cell
• Key functions include growth, repair, and asexual reproduction
• The cell cycle includes interphase (G1, S, and G2 phases) and the mitotic (M) phase
• Interphase involves cell growth and DNA replication in preparation for mitosis
• Mitosis has several phases, including prophase, prometaphase, metaphase, anaphase, and telophase
• Cytokinesis, the division of the cytoplasm, typically occurs immediately after mitosis

Phases of Mitosis

• Prophase: Chromatin condenses into visible chromosomes; the nuclear envelope breaks down, and the mitotic spindle forms
• Prometaphase: The nuclear envelope fully dissolves, and spindle microtubules attach to the kinetochores of chromosomes
• Metaphase: Chromosomes align along the metaphase plate, also known as the equator of the cell
• Anaphase: Sister chromatids separate and move to opposite poles of the cell, pulled by the shortening of the microtubules
• Telophase: Chromosomes arrive at the poles, the nuclear envelope reforms around each set of chromosomes, and the chromosomes decondense
• Cytokinesis: The cytoplasm divides, resulting in two separate daughter cells
• In animal cells, cytokinesis involves the formation of a cleavage furrow
• In plant cells, a cell plate forms to divide the cell

Significance of Mitosis

• Genetic continuity is ensured by producing identical daughter cells
• Mitosis is crucial for growth, repair, and asexual reproduction

Meiosis

• Meiosis reduces the chromosome number by half, resulting in four haploid daughter cells
• It is essential for sexual reproduction because it produces gametes, such as sperm and egg cells
• Meiosis involves two rounds of cell division: meiosis I and meiosis II
• DNA replication occurs during interphase before meiosis

Meiosis I

• Prophase I: Chromosomes condense, and homologous chromosomes pair up to form tetrads, also known as bivalents
• Crossing over occurs, where genetic material is exchanged between homologous chromosomes
• Metaphase I: Tetrads align along the metaphase plate
• Anaphase I: Homologous chromosomes separate and move to opposite poles
• Sister chromatids remain attached
• Telophase I: Chromosomes arrive at the poles, and the cell divides, resulting in two haploid cells

Meiosis II

• Prophase II: Chromosomes condense again
• Metaphase II: Chromosomes align along the metaphase plate
• Anaphase II: Sister chromatids separate and move to opposite poles
• Telophase II: Chromosomes arrive at the poles, and the cell divides, resulting in four haploid daughter cells

Genetic Variation in Meiosis

• Crossing Over: Exchange of genetic material between homologous chromosomes increases genetic variability
• Independent Assortment: Random orientation of homologous chromosomes during metaphase I leads to different combinations of chromosomes in daughter cells
• Random Fertilization: Any sperm can fuse with any egg, further increasing genetic variation

Significance of Meiosis

• The chromosome number is reduced by half, ensuring that offspring have the correct number of chromosomes upon fertilization
• Genetic variation is introduced, which is essential for evolution and adaptation

Mitosis is a cell division process resulting in two identical daughter cells. It's crucial for growth, repair, and asexual reproduction. The process includes interphase and distinct phases like prophase, metaphase, anaphase, and telophase.