- Understand the importance of cell division in growth and reproduction.
- Outline the processes of meiosis.
Meiotic cell division (Meiosis)
- Meiosis is the nuclear division that a parent cell divides into four daughter cells with number of chromosomes is half of the parent cell.
HKDSE Biology students have to remember how chromosomes are arranged in different phases of meiosis ❗️ ❕
👆🏻This photo showing different phases in meiosis.
1. Prophase I
- = Prophase in mitosis
- Homologous chromosome undergo condensation.
- The homologous chromosome consisting two chromatids joined together by centromere.
- Meiotic spindle is generated on each side.
2. Prometaphase
- = Prometaphase in mitosis
- The nuclear membrane breaks down.
- Meiotic spindle formed in prophase will attach to the centromere of homologous chromosome.
3. Metaphase I
- Meiotic spindle pull the homologous chromosome till they align in a plane.
- The homologous chromosome pairs are located at the centre of the cell due to the movement of mitotic spindle.
- ⭐️ instead of only one of each homologous chromosome in each row like mitosis, homologous chromosome pairs located in the same row in meiosis.
4. Anaphase I
- Paternal chromosome (father) and maternal chromosome (mother) in the homologous chromosome are separated at their centromeres.
- Paternal chromosome (father) and maternal chromosome (mother) are pulled to opposite poles of the cell by meiotic spindle randomly.
5. Telophase I (2n - diploid)
- The nuclear membrane forming back.
- The nuclear membrane enclosing each set of chromosome for each daughter cell.
- ⭐️ Chromosomes will not uncoil and become less compact in Telophase I.
First cytokinesis occurred after telophase I to separate the parent cell into two daughter cell. ✌🏻
👆🏻This photo showing the situation of cell under meiosis I.
6. Prophase II
- = Prophase I
7. Prometphase II
- = Prometaphase I
8. Metaphase II
- Meiotic spindle pull the maternal or paternal chromosome till they align in a plane.
- The maternal and paternal chromosome are located at the centre of the cell due to the movement of mitotic spindle.
9. Anaphase II
- Chromatids in chromosome are separated at their centromeres.
- Chromatids are pulled to opposite poles of the cell by meiotic spindle.
10. Telophase II (n - haploid)
- The nuclear membrane forming back.
- The nuclear membrane enclosing each set of chromosome for each daughter cell.
- Chromosomes start to uncoil and become less compact again.
Second cytokinesis occurred after telophase II to separate the two daughter cells in telophase I to four daughter cells. ✌🏻✌🏻
👆🏻This photo showing the situation of cell under meiosis II.
Importance of meiosis 💫
- Sexual reproduction - formation of sex cells and gamete (ovum and sperm).
- Maintenance of constant number of chromosome in organism - offsprings will restored after the fusion of female haploid gamete and male haploid gamete.
- Enhancement of genetic variation - crossing over is occured during meiosis.
That'd the end of this topic
References
- Meiosis - Stages - Clinical Relevance. (n.d.). Retrieved from https://teachmephysiology.com/basics/cell-growth-death/meiosis/
- Admin. (2019, February 11). Significance of Meiosis-Definition, Features and Significance. Retrieved from https://byjus.com/biology/significance-of-meiosis/