21/09/2026
Form 3 Biology - Genetics (Meiosis and Mitosis)
1. What is the primary purpose of meiosis?
• to produce haploid gametes (s***m and eggs) with half the number of chromosomes found in somatic cells.
2. How many rounds of cell division occur during meiosis?
• Two rounds of cell division occur during meiosis: meiosis I and meiosis II.
3. What is crossing over, and when does it occur during meiosis?
• Crossing over is the exchange of genetic material between homologous chromosomes. It occurs during prophase I of meiosis.
4. What are homologous chromosomes?
• Homologous chromosomes are chromosome pairs (one from each parent) that carry the same genes, although they may have different versions (alleles) of those genes.
5. How does meiosis contribute to genetic diversity in offspring?
• Meiosis leads to genetic diversity through independent assortment of homologous chromosomes during meiosis I and random segregation of sister chromatids during meiosis II.
6. What is the primary purpose of mitosis?
• to produce two genetically identical daughter cells from a single parent cell for growth, tissue repair, and asexual reproduction.
7. What are the main stages of mitosis, and in what order do they occur?
• in order of prophase, metaphase, anaphase, and telophase.
8. How does cytokinesis differ between animal and plant cells during mitosis?
• In animal cells, cytokinesis occurs through the formation of a contractile ring that pinches the cell membrane inward. In plant cells, a cell plate forms between the daughter cells and eventually develops into a new cell wall.
9. What is the importance of maintaining the same chromosome number in daughter cells after mitosis?
• Maintaining the same chromosome number ensures that the genetic information remains stable and consistent in each new cell, preserving the species' characteristics.
10. What is the significance of meiosis in sexual reproduction?
• Meiosis is essential for sexual reproduction because it produces haploid gametes with genetic diversity. When gametes fuse during fertilization, the resulting zygote has a unique combination of genetic material from both parents.
11. Describe the key events that occur during prophase I of meiosis.
• During prophase I of meiosis, homologous chromosomes pair up to form tetrads, and crossing over occurs, where genetic material is exchanged between non-sister chromatids. The nuclear envelope begins to break down, and spindle fibers start to form.
12. What is nondisjunction, and how does it relate to meiosis?
• Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during meiosis. This can result in gametes with abnormal chromosome numbers, leading to conditions like Down syndrome.
13. How does the number of chromosomes change during meiosis?
• The number of chromosomes is halved during meiosis. In humans, diploid cells (2n) containing 46 chromosomes become haploid cells (n) with 23 chromosomes after meiosis.
14. Explain the role of the spindle fibers during mitosis.
• Spindle fibers are responsible for separating sister chromatids during anaphase. They attach to the centromere of each chromatid and pull them toward opposite poles of the cell.
15. How does mitosis contribute to growth and tissue repair in multicellular organisms?
• Mitosis allows for the production of identical daughter cells, which replace damaged or worn-out cells and contribute to the growth and repair of tissues in multicellular organisms.
16. What would happen if a cell undergoes mitosis without completing interphase?
• Interphase is crucial for cell growth, DNA replication, and preparation for mitosis. Without completing interphase, the cell may not have enough genetic material, organelles, or energy to divide properly.
17. Why is mitosis considered a conservative form of cell division?
• Mitosis is considered conservative because the genetic content of the parent cell is preserved in the daughter cells. Each daughter cell receives an identical set of chromosomes as the parent cell.
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