Understanding Meiosis: The Process of Genetic Variation
Exploring the Key Stages and Differences between Asexual and Sexual Reproduction
Introduction: Asexual and Sexual Reproduction
- All organisms reproduce to add new individuals to the population
- Reproduction occurs through asexual or sexual modes
- Lower organisms prefer asexual reproduction through mitosis
- Sexually reproducing organisms use meiosis to increase their population
The Interface: Preparatory Phase
- Cell goes through G1, S, and G2 phases to grow and prepare for division
- Genetic material (DNA) is replicated during interphase
- Centrosome duplication is important for spindle fiber formation
Meiosis I: Prophase I and Metaphase I
- Prophase I is the longest phase with sub-stages: leptotene, zygotene, pachytene, diplotene, and diakinesis
- Crossing over occurs during pachytene, resulting in genetic recombination
- Metaphase I sees alignment of homologous chromosome pairs on the equator
Meiosis I: Anaphase I and Telophase I
- Anaphase I separates homologous chromosome pairs
- Telophase I involves nuclear membrane formation and cytokinesis
- Two haploid cells are formed at the end of Meiosis I
Meiosis II: Prophase II and Metaphase II
- Prophase II involves condensing of chromosomes and disappearance of nuclear membrane
- Metaphase II sees alignment of chromosomes on the equator again
Meiosis II: Anaphase II and Telophase II
- Anaphase II separates sister chromatids
- Telophase II involves nuclear membrane formation and cytokinesis
- Four haploid cells (gametes) are formed at the end of Meiosis II
Mitosis vs Meiosis: Key Differences
- Mitosis results in two identical diploid cells
- Meiosis results in four genetically diverse haploid cells
- Meiosis involves genetic recombination through crossing over