Recording-2025-02-25T17:29:32.425Z

Types of Cell Division

• Two primary types of cell reproduction: Mitosis and Meiosis.

Mitosis

• Type of cell division responsible for growth and maintenance in organisms.

• Starts with one parental cell and divides to produce two daughter cells.

• Each daughter cell is genetically identical to the parental cell (clones).

• DNA duplication is essential before division to ensure each daughter cell receives a complete copy of genetic material.

• Used for replacing damaged or lost cells, such as skin and blood cells.

• For example, human blood cells have a short lifespan of approximately four months and are continuously replaced through mitosis.

• In organisms like sea stars, mitosis allows regeneration of lost body parts.

Process of Mitosis

1. Interphase: 90% of a cell's lifespan is spent here, preparing for division:

   • G1 Phase: Growth phase, where the cell increases in size.

   • S Phase: Synthesis phase, where DNA is replicated.

   • G2 Phase: Final growth phase, preparing for mitotic division.

2. Mitosis Phases:

   • Prophase: Chromatin condenses into visible chromosomes. Nuclear envelope begins to break down.

   • Metaphase: Chromosomes align at the metaphase plate.

   • Anaphase: Sister chromatids separate and move to opposite ends of the cell.

   • Telophase: Chromosomes reach the poles, nuclear envelope reforms, and the cell prepares to split.

3. Cytokinesis: The physical division of the cytoplasm occurs, resulting in two daughter cells.

   • In animal cells, this forms a cleavage furrow.

   • In plant cells, a cell plate forms to separate the two new cells.

Meiosis

• A specialized type of cell division that produces gametes (sex cells) for sexual reproduction.

• Meiosis results in four non-identical daughter cells, each with half the number of chromosomes of the parental cell (haploid).

• In humans, this process produces sperm and egg cells (gametes).

• Critical for genetic diversity in sexually reproducing organisms through the process of fertilization, where male and female gametes fuse.

• Begins with a diploid parental cell and goes through two rounds of division (Meiosis I and Meiosis II).

Genetic Material

• DNA consists of genes containing information for producing proteins.

• Human cells have 46 chromosomes, which include genetic information inherited from both parents.

• The sex chromosomes (X and Y) determine gender:

  • XX: Female

  • XY: Male.

• Each chromosome contains many genes, and during cell division, chromosomes condense into visible structures.

Chromosome Structure

• Chromosomes consist of two halves called sister chromatids, which are identical copies formed during DNA replication.

• Following mitosis, the daughter cells each receive one chromatid from each chromosome, ensuring genetic continuity.

Summary of Reproductive Strategies

• Asexual Reproduction:

  • Involves production of new individuals without the fusion of gametes.

  • Common in single-celled organisms like bacteria, which reproduce by binary fission (a form of mitosis).

  • Some multicellular organisms can also reproduce asexually, like certain plants and sea stars.

• Sexual Reproduction:

  • Involves the fusion of egg and sperm (gametes), resulting in genetic variation among offspring.

  • Meiosis is crucial for producing haploid gametes during sexual reproduction.

Conclusion

• Cell division is essential for growth, repair, reproduction, and maintaining genetic continuity.

• Mitosis allows for asexual reproduction and cell regeneration, while meiosis enables sexual reproduction and genetic diversity.