Meiosis
Chapter 1: Introduction to Meiosis
- Meiosis is a type of cell division that produces four genetically different daughter cells, each with half the number of chromosomes of the parent cell.
- This process underpins sexual reproduction, as it creates sperm cells in males and egg cells in females.
Chapter 2: Phases of Meiosis
- Meiosis consists of two successive divisions, namely Meiosis I and Meiosis II, each with different phases.
- Meiosis I contains four phases: Prophase I, Metaphase I, Anaphase I and Telophase I.
- Meiosis II also contains four phases: Prophase II, Metaphase II, Anaphase II and Telophase II.
- By the end of Meiosis II, four haploid daughter cells are produced.
Chapter 3: Crossing Over and Genetic Variation
- Crossing over is the exchange of genetic material between homologous chromosomes during the prophase I of meiosis.
- This process contributes to genetic variation, as it mixes up the parental genes.
- Independent assortment of chromosomes during Meiosis I also contributes to genetic variation.
- The variety in the combination of genes can have an impact on the traits exhibited by offspring.
Chapter 4: Difference between Mitosis and Meiosis
- Unlike mitosis, which creates two identical cells, meiosis produces four genetically different cells.
- The cells produced by mitosis have the same number of chromosomes as the parent—it is a process of asexual reproduction.
- Meiosis is a longer process than mitosis as it has two rounds of division. The resulting cells have half the pair of chromosomes.
Chapter 5: Role of Meiosis in Evolution
- Meiosis, due to the genetic variation it generates, plays a crucial role in evolution.
- Different gene combinations produced by crossing over and independent assortment during meiosis allows for genetic diversity in populations.
- Genetic diversity is critical to evolution as it enables a species to adapt to changes in the environment.
Chapter 6: Disorders due to Errors in Meiosis
- Errors during meiosis, such as nondisjunction, can lead to genetic disorders.
- Nondisjunction is when chromosomes fail to separate properly, resulting in an abnormal number of chromosomes in the resulting daughter cells.
- This can lead to conditions like Down Syndrome, Turner’s Syndrome, or Klinefelter’s Syndrome, all of which are characterised by an abnormal number of chromosomes.