Mitosis and Meiosis reviewer

• Mitosis


  1. Describe the process

  2. Explain the importance in the human body

  3. Enumerate the stages
• Third tenet of cell theory: Cell come from pre-existing cells
• No new cells will be formed without pre-existing cells
• Cellular Reproduction is essential in perpetuation of life
• Cell division (Unicellular)


  A means to produce offspring
• Cell division (Multicellular)


  A means to produce new tissues or body parts during growth and development
• Types of cell division

  • Mitosis
  • Meiosis

  
• Mitosis


  • Produces 2 diploid daughter cells
  • One division

  
• Meiosis


  • Produces 4 haploid daughter cells
  • Two divisions
• The cell cycle


  1. Interphase (G1, S, G2)

  2. Mitosis

  
• Interphase: G1 phase


  Cell is young, undergoes rapid growth, organelles form, cellular contents (except chromosomes) are duplicated
• Interphase: G1 checkpoint


  Ensures cell is ready to undergo DNA synthesis or S phase
• Interphase: S phase


  DNA doubles through replication, DNA is duplicated and ready for chromosome formation in M phase

  
• Interphase: G2 phase


  Preparation for cell division, ATP produced in large amounts
• Interphase: G2 checkpoint


  Makes sure cell is mature enough to undergo M phase
• M phase: Mitosis


  1. Chromosomes appear

  2. Centrioles separate and spindles form

  3. Chromosomes line up at metaphase plate

  4. Sister chromatids divide and move to opposite poles

  5. DNA uncoils, nuclear membrane forms, spindle fibers dissolve

  6. Cell membrane pinches in to form 2 new daughter cells

  
• Chromosomes


  DNA code read like a book, bases form the alphabet, groups of 3 bases code for an amino acid, a long string of amino acids makes a protein, each gene is a set of instructions for making a protein
• Cell cycle checkpoints


  Ensure cell is ready to proceed, detect abnormalities and instruct cell to repair or undergo apoptosis
• Cell cycle checkpoints not fully functioning can lead to cancer
• Interphase - summary


  1. Makes new organelles

  2. DNA is replicated

  3. Cells increase in size
• Mitosis


  The part of cell division which results in two identical daughter cells from a single parent cell

  
• Mitosis - functions


  • Growth and development
  • Repair

  
• Stages of mitosis


  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
• If cells divide non-stop, it can lead to cancer
• Meiosis


  The process of cell division that produces haploid gametes (half the number of chromosomes)
• Meiosis


  • Occurs only in gonads (testes and ovaries)
  • Produces gametes (sperm or egg)
  • Similar to mitosis in several ways but results in haploid daughter cells

  
• Stages of meiosis I

  • Prophase I
  • Metaphase I
  • Anaphase I
  • Telophase I

  
• Meiosis I


  Halves the number of chromosomes from diploid to haploid number (reductional division)
• Meiosis II


  Similar to mitosis (equational division)

  
• Interphase in meiosis


  Chromosomes replicate, each duplicated chromosome consists of identical sister chromatids

  
• Prophase I in meiosis

  Chromosomes condense, synapsis occurs (homologous chromosomes come together to form a tetrad)
• Crossing over


  Exchange of genetic material between homologous chromosomes, occurs at chiasmata
• Independent assortment


  Random orientation of homologous pairs to poles, results in variation
• Meiosis II


  No interphase II, similar to mitosis with 4 phases: Prophase II, Metaphase II, Anaphase II, Telophase II