Nuclear Division Prevents Anucleate Cells
- Before a cell divides, its nucleus must divide first to ensure each daughter cell receives a complete set of genetic instructions.
- Without nuclear division, one daughter cell would lack a nucleus (anucleate) and be unable to function.
- Red blood cells are anucleate and survive only about 120 days.
- This is because they cannot produce proteins or repair themselves.
Mitosis Maintains the Chromosome Number and Genome
Definition
Mitosis
Mitosis is a type of cell division in which a single parent cell divides to produce two genetically identical daughter cells, each containing the same number of chromosomes as the parent cell.
- Mitosis is crucial for:
- Growth: Multicellular organisms grow by adding new cells through mitosis.
- Repair: Damaged tissues are repaired by replacing lost or injured cells.
- Asexual Reproduction: Eukaryotic organisms such as some protists and plants reproduce by mitosis. (Note: Bacteria use binary fission, not mitosis.)
How Mitosis Works
The diagram shows the process using one homologous pair (pink and blue chromosomes):
- DNA copied: Before mitosis begins, DNA replicates. Each chromosome now consists of two identical sister chromatids joined at the centromere.
- Mitosis: The sister chromatids separate and move to opposite ends of the cell.
- Result: Two daughter cells, each containing one pink chromosome and one blue chromosome, identical to the parent cell.
Mitosis ensures continuity
Why Mitosis Matters
- Mitosis ensures that every cell in a multicellular organism has the same genetic information.
- This uniformity is vital for maintaining the organism's structure and function.
In plants, mitosis in the apical meristems allows roots and shoots to grow, while in animals, it replaces worn-out skin cells.
Meiosis Halves the Chromosome Number and Generates Genetic Diversity
Definition
Meiosis
Meiosis is a type of cell division that reduces the chromosome number by half, producing four genetically distinct haploid cells. This process occurs in gamete-producing cells and is essential for sexual reproduction.
