Cell division

• Mitosis definition


  Cell division is when 1 cell splits in half to form 2 new cells. Original cell = parent cell and new cells = daughter cell. Essential for growth, development, and tissue repair in multicellular organisms
• Mitosis Phases


  P(rophase)

  M(etaphase) - Middle

  A(naphase) - Apart

  T(elophase) - Two
• Cell Cycle 


  Interphase: Cellular growth and duplication of chromosomes

  Mitosis: Separation of sister chromatids and formation of two new nuclei

  Cytokinesis: Division of cytoplasm and formation of two new daughter cells

  
• P - PROPHASE


  Spindle fibers form, chromatin condense into chromosomes at centromere, centrioles move to opposite sides to form poles

  
• M - METAPHASE


  Nucleus disappears. Chromosomes line up in the middle of cell. Spindle fibers connect to chromosomes. Centromeres of each chromosome attach itself to a spindle

  
• A - ANAPHASE


  Spindle fibers pull chromosomes to opposite poles. Separated chromatids (filled with genetic info) are pulled to opposite sides of pole

  
• T - TELOPHASE 


  Chromosomes uncoil. 2 new nuclei are formed. Spindle fibers disappear

  
• Cytokinesis 


  Cytoplasm divides with exact organelles and forms two daughter cells
• Meiosis Definition


  Meiosis is a cell division that occurs in sexually reproducing organisms. Unlike mitosis, which produces two genetically identical daughter cells, meiosis produces four daughter cells. We use it to produce gametes (sperm + egg cells)
• Meiosis Step 1: Replicating DNA


  Before meiosis parent cell replicates DNA. DNA condenses into chromosomes
• Meiosis Step 2: Breakdown of Nuclear Membrane


  Nuclear membrane breaks down and homologous chromosomes pair up and move to equator of the cell. Network fibers separate homologous chromosomes. Homologous contain a maternal and paternal copy of same chromosome. Each side of cell receives one maternal/paternal copy

  
• Meiosis Step 3: Nuclear Membranes Reform

  Nuclear membranes reforms around separated chromosomes. Cell membrane pinches off to make two daughter cells. Daughter cells are haploid with mixture of paternal + maternal characteristics.

  
• Meiosis Step 4: Round 2

  Daughter cells go for another round of cell division. Nuclear membranes break down again and chromosomes align at equator of cell. Fiber network separates the sister chromatids

  
• Meiosis Step 5: The End


  Nuclear membranes form at each end of the cells and the cell membranes pinch the cells in half. This produces four haploid daughter cells called gametes. Meiosis is finished.

  
• Gametes


  Gametes are a product of meiosis. Gametes are the only haploid cells in body, one copy of each chromosome. All other cells have 2 copies, making them diploid

  
• Fertilisation


  Sexual reproduction = sperm and egg cell fuse process is fertilisation. Fusion of sperm and egg cell creates a zygote.
• Zygote


  Because the male and female gametes fuse to form the zygote, the zygote inherits all of the chromosomes from each gamete. This gives the zygote a two copies of each chromosome and makes it diploid.

  
• Comparing Cell Cycles


  In meiosis, the homologous chromosomes are separated in the first round of cell division, and the sister chromatids in the second. In mitosis, only the sister chromatids are separated. Additionally meiosis produces four haploid daughter cells while mitosis produces two diploid daughter cells. Mitosis for growth and recovery, meiosis for sexual reproduction.